CN1024961C - Methods used to transmit signals and data - Google Patents

Abstract

A communication device that transmits data between multiple peripheral devices and a host computer. On the bus, only one device at a time can execute said commands and only respond to commands from the host computer. When an external device needs service, it signals a service request by holding the bus low after either command. The device continues to issue service requests until it receives a command from the host computer. When more than one device of the same type is coupled to the bus (eg, two mice), the host computer assigns a new address to the device. When a device wants to send a "1", it sends a low signal to the bus to detect a collision.

Description

The present invention relates to the field of communication devices for transmitting data between a data source and a plurality of external devices coupled thereto. More particularly, the present invention relates to data transfer on an external standby bus between a plurality of external devices and a host computer.

In the computer industry, it is often necessary to transfer data and commands between multiple data processing devices (such as computers, printers, storage, etc.). In the early 1970s, due to the advent of computer network systems, the interconnection between computers and other external devices has undergone important development. Computer network systems enable distributed access to computing resources away from mainframe computers.

Networks, such as the ARPA network, are primarily used to provide different users access to larger time-sharing systems and data transmission between such systems. In a geographically local network, called a "local area network" (LANS), it is used to connect a group of computers, terminals and their external devices, usually in one building or adjacent buildings, so that these devices can communicate with each other. communication. Distributed computing can be achieved using local area networks. In other words, certain devices connected to the local area network can be designated to perform specific functions, such as file storage, database management, terminal processing, and so on. This distributed processing makes the system simpler and more efficient as different machines perform different tasks.

Currently, networking technologies are only used to provide communication between data processing devices, which are machine input devices. However, networking technology can also be used to provide networked devices for communicating between a single computer and multiple external devices, such as manual input devices, listen only clevice, and appliances. Manual input devices include keyboards, cursor control devices (such as mouse cursors) and sketchpads, among others. Listen-only devices include transaction log and more. In the prior art, these devices are Connect to the host computer through a designated port on each device. To interface external input devices, additional "boards" are often required. When inserting the additional board, the main computer is also required to be powered off, and it cannot be inserted when the system is working. This prior art system is not efficient because usually the external devices do not work simultaneously. (A user using a mouse, for example, would not normally be using a keyboard or drawing pen at the same time.) Therefore, these devices can share a common line to the host computer without additional boards and without causing data transfer problems.

Prior art network designs also include good methods of establishing network control to enable transmission by a certain device. When networking external devices, such a system is not required, since usually only one device is in use at a time. In addition, prior art network designs allow networked devices to identify each other through complex "lookup" methods. On the other hand, such complicated procedures are unnecessary for connecting external devices, since these devices themselves do not need to be recognized by other devices except the host computer.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide communication means between a plurality of peripheral devices which allow simple and efficient coupling of those devices to a host computer.

Another object of the present invention is to provide communication means for coupling all of the aforementioned peripheral devices to a host computer through a single input port.

It is still another object of the present invention to provide communication means by which an external device can indicate a service request signal to a host computer.

Yet another object of the present invention is to provide a communication link providing means for determining whether the link of the communication device is occupied.

Another object of the present invention is to provide communication means enabling external equipment to join while the system is in operation.

A communication device for transferring data between a plurality of peripheral devices and a host computer is disclosed, including an apparatus and a method. In a preferred embodiment, multiple external devices, such as manual input devices (including mouse pointers, keyboards, sketchpads, etc.), meters, listen-only devices, etc., are coupled to a common cable to transmit data and receive commands . When the equipment coupled to the cable requires When it needs to be serviced, it can notify the host computer, and the device will continue to send out service requests until it receives a command to send data from the host computer. All the same general-purpose external devices (such as all keyboards) have the exact same hardware jumper address as the identification code. In this way, the host computer can identify the general-purpose devices communicating on the cable. If more than one of the same type is externally coupled to the cable (for example, there are two mice), the host computer will assign new addresses to the status registers of the mice so that they are distinguishable from each other.

In the preferred embodiment, return-to-zero modulation is used to transmit data and commands over the cable. This makes it so that if an external device transmits a high signal on the cable while the cable is being pulled low by another device, the external device will crash. To simplify the system model, only the host computer can initiate the communication process.

The invention allows external devices to be connected to the computer without powering off the computer system while the computer is working. The present invention can be implemented in narrowband, broadband, optical fiber, far infrared and other communication devices.

Figure 1 shows a block diagram of the network system of the present invention.

FIG. 2 shows a timing diagram of the return-to-zero encoding method used in the present invention.

Figure 3 shows the registers of the peripheral device of the present invention.

Figure 4 shows the flow of the operation sequence when an external device requests the service of the host computer.

Figure 5 shows a flow chart of the sequence of operations for providing a new address to a device that shares a hardware jumper address.

FIG. 6 shows a sequence diagram of command processing in the present invention.

Fig. 7 is a flow chart illustrating the sequence of operations for activating an external device.

The present invention discloses a peripheral bus for transferring data between peripheral devices coupled to a host computer, including apparatus and methods therefor. In the following description, numerous specific details are given in order to provide a thorough understanding of the present invention, such as specific numbers, registers, addresses, timings, signals, and formats. It will be apparent, however, to one skilled in the art that these specific details may be practiced without these specific details. In other cases, in order to avoid unnecessary In order not to obscure the present invention, well-known circuits and devices are shown in block diagram form.

Referring to Figure 1, a preferred example of the present invention is shown. A plurality of external devices, identified by numerals 11 to 16 , are coupled to the host computer 10 by a single cable 17 . In the preferred example, the device communicates with the host computer through a miniature telephone jack having connectors as specified below. Top power (tip-power), ring-data (ring-data) and sleeve-return power (sleeve-power return). A high signal (1) has a minimum of 2.4 volts and a low signal (0) has a maximum of 0.8 volts. Although it is desired to use a single cable in the preferred practice of the invention, other communication means such as broadband methods, fiber optic systems and infrared signals may also be used.

The bus in the present invention has supported coding equipment (one key of this equipment represents a symbol or a kind of function, as keyboard 14), relative equipment (the corresponding control equipment of this equipment (as mouse type scaler 11 or 12) The movement of display cursor can start from any point) and absolute device (there is a constant direct relationship between the display position of this device, such as drawing pen 13.)

This system also allows extended address devices to be networked. Extended address devices share a common hardware jumper address 25, but there is a unique address for a specific device, and the host computer needs to identify this address before accessing the device. As shown in block 201 of FIG. 7, each extended address device has a unique extended address. For example, it is contemplated that the meters could be coupled to and controlled by a host computer. In this case, all meters have the same fixed hardware jumper address. At the first level, the host computer will simply address the hardware jumper addresses of these meters. As shown in block 203 of FIG. 7, the command from the host computer is transferred to the fixed hardware jumper address of the extended address device. At this time, all meters connected to this address are in an invalid state. If the host computer sends a signal to a meter, and this number matches the extended address of the meter, the meter is made active by the host computer. An extended address is an identifier. In the preferred embodiment, the extended address can be as long as 64 bytes. As shown in block 205 of FIG. 7, the device is activated by sending the extended address of the device. As long as the host computer gives the extended address, the device with this address enters the valid state. The commands sent to the instrument address area in the future will be executed by this device, and it is not necessary to give the extended address every time. As shown in block 207 of Figure 7, sending a fixed The hardware jumper address device makes the extended address respond. A valid meter executes all commands to the meter's address, while an invalid device is passive. In order to make a valid extended address device invalid, the host computer only needs to give the extended address of another extended address device to make it valid, and at the same time make the original valid device invalid. Fixed hardware jumper addresses 21a, 21b, 23 and 24 are shown in FIG. 1 for mouse 11, mouse 12, sketch pad 131 and keyboard 14, respectively. It is assumed that any device that can be controlled by the host computer is suitable for this network design, such as electric lights, electric furnaces, sprinkler irrigation systems, and telephone answering machines. It is assumed that there is at least one hardware jumper address of another extended address device in this system, this address will be used for system protection or user identification. For example, a certain device at this address can have an extended address, and the system can work only after the system user gives this extended address. In other cases, certain individual operations may require the host computer to give the extended addresses of other security devices before execution. These security devices act like "keys" that lock the entire system or certain operations performed on the system.

In addition, the present invention reserves the soft address segment 16 for network applications. The reserved soft address segment is used when the same external device is coupled to the bus. For example, if more than one mouse scaler is coupled on the bus, the host computer assigns new addresses to each mouse scaler, and these addresses are placed in the soft address segment. Although specific examples are given for each type of device coupled to the bus, there may be more than one type of device for which addresses are assigned. For example, the sketch pad is an absolute device, and the touch screen is also an absolute device, and it has the same fixed command address as the drawing pen. At this time, the host computer will assign a new address to each device in the soft address segment.

In a preferred embodiment of the present invention, the address allocation of a plurality of external devices is as follows:

Address Device Type Example

0000 (0) extended address device security system, user ID

0001 (1) Extended Address Device Meter

0010 (2) Coding equipment Keyboards

0011(3) relative device mouse scaler

0100 (4) Absolute Equipment Sketchpad, touch screen

0101(5) Reserved None

0110(6) Reserved None

0111(7) Reserved None

1000 (8) soft address addressing the same external device

... ... ... ... ...

1111 (15) Soft address addressing Same external device

Those skilled in the art will realize that other addresses can also be assigned to these devices, and the digits of these addresses can be more or less than those in the embodiment.

In this preferred embodiment, all external devices have four registers for receiving and sending data. For each device, the talk register 3 and listen register 3 contain status information such as device address, handler information. The remaining registers are all data registers, except for the listening register 2, which are proprietary devices, and the listening register 2 contains the extended address of the extended address device or the device-specific information of the soft address addressing device.

In the preferred embodiment of the invention, there are three types of communications on the external bus, namely command, data and global signals. The command is transmitted from the host computer to the external device; the data is transmitted from the host computer to the external device or from the external device to the host computer; the whole signal is the special information transmitted to the whole system.

In the preferred embodiment, data is encoded as a ratio of low time to high time per bit. A bit boundary is defined as a falling edge on the bus. A zero is encoded as a bit whose low time is greater than the high time, as shown by bit 20 in FIG. 2 . "1" is defined as a bit whose low level time is shorter than the high level time, as shown in bit 21 in FIG. 2 . In this preferred embodiment, the start bit is defined as "1", the stop bit is defined as "0", and the stop bit has no additional falling edge to define the bit time. The stop bit is used to synchronize the termination of a transaction on the bus.

The bit period of command signals and low-speed data transmission is about 100 microseconds ± 30%. The bit rate for high-speed data transmission is 50 microseconds ± 1%. The format of data processing is the start bit (1), followed by up to 256 data bits, and finally the stop bit. When using other communication devices, you can use other signal formats.

Commands can only be sent by the host computer. In the preferred embodiment of the invention, there are three commands: talk, listen and clear. As shown in Figure 6, in order to indicate the beginning of the command, a prompt pulse is given first, and the prompt pulse is generated by the host computer through the bus for low-level transmission in the "T-attn" period. In this preferred embodiment, the T-attn period is about 560-1040 microseconds. The prompt pulse is followed by a sync pulse, which is used to start the bus sequence. The trailing edge of the sync pulse is used as the timing reference point for the first bit. The command is followed by a stop bit ("0" in this embodiment). After the stop bit, the bus returns to its normal high state if there are no service requests from other devices.

In the preferred embodiment, the command is an 8-bit value. This command contains a 4-bit device address segment specifying the fixed hardware jumper address of the required external device (such as the address of the mouse scaler is 0011). The next two are commands, and the last is a two-bit register address segment, which provides a special register R0-R3 in the selected external device to be specified. In this preferred embodiment, the command code is as follows:

command code

Clear 01

listen 10

say 11

The speaking command makes the selected device transmit its data to the host computer, and the listening command makes the selected device receive the data from the host computer and store it in its register. The clear command has an effect on each device defined by the special device, and it can be used to clear registers or reset all keys on the keyboard for resend.

When an external device is selected to execute a speaking command, the device must respond within a certain period of time, which is called a "time out" period. The time out period "Tlt" has a large dimension of 140-260 microseconds (2 bits). If the selected device does not exceed the time, it will become valid on the bus, perform data transmission, then end the command execution, and return to the invalid state on the bus.

Global signals are used for process processing that is neither commands nor data. The whole signal includes: reminder and synchronization signal, used for start command and bus timing; service request signal, used for device to master The computer requests service; the reset signal makes the bus low within the minimum value of Tres to generate an interrupt on the bus. Tres period is about 2.8-5.2 microseconds (40 bits). Global signals will be described in detail along with other processing.

Since an external device can only send data after receiving a command from the host computer, this system provides a method for the device to notify the host computer that it needs service, which is realized by the device sending a service request signal to the host computer. In the present invention, sending the service request signal is to keep the bus at low level after the stop bit of any command processing. Each external device coupled to the bus has a number of registers (four registers in the preferred embodiment), and Figure 3 shows one register for the external device. Bit A13 is the service request enable bit. When this bit is set to high level by the host computer and needs service, the device can make the bus at low level after the stop bit of command processing, as shown in Figure 6. The device will continue to issue service requests until it receives a command from the host computer. The flowchart in Fig. 4 shows the processing steps after the device requests the service.

Initially, the device determines whether it requests service (see box 41 of Figure 4), ie whether it has data to transmit to the host computer. If there is data to transmit, the device sets its internal flag bit (as shown in block 42 of Figure 4). When the host computer issues the next command (as shown in block 43 of Figure 4), the device checks to see if this is the command addressed to it (as shown in block 44 of Figure 4). If the command does not select this device (as shown in block 45 of Figure 4), the device will check whether its service request enable bit (A13 bit of register 3) is set to a high level (as shown in block 47 of Figure 4). If it is high (as shown in branch 48 of block 4 of FIG. 4), the device takes the bus low (as shown in block 50 of FIG. 4) after commanding the stop bit, see FIG. The device then waits to receive the next host computer command, checking to see if it is selected to execute said command (as shown in block 43 of Figure 4). If the command selects this device (as shown in the branch 46 of Figure 4), it will determine whether to speak the command (as shown in the frame 51 of Figure 4), if not say the command (as shown in the frame 52 of Figure 4), The device sends a service request (as shown in frame 57 of Figure 4), executes the command received (as shown in frame 58 of Figure 4), and then waits for the next command (as shown in frame 43 of Figure 4); if it is said Command (as shown in the branch 53 of Figure 4), the device sends data (as shown in the box 59 of Figure 4), and considers that the service request has been satisfied (as shown in the box 60). The device continues to monitor its own status to decide when service is required (as shown in block 41 of Figure 4). More efficient operation on the bus is achieved by enabling the host computer to control the service request enable bit. After receiving the service request, the host computer only needs to check whether the device whose service request enable bit is set needs service. Additionally, the host computer can disable certain devices that are not required for a particular application.

When transferring data, the device can detect collisions. If the external device is outputting a 1 and the data line is 0 or is about to go to 0, the device is considered to have had a collision with another device. This means that another device is also transmitting data on the bus. When this happens, the bumped device stops executing commands on the bus and keeps sending data for retransmission. When a collision occurs, the device sets its internal flag bit. In the prior art, external devices cannot detect collisions. This novel feature of the present invention makes communication operations more efficient. By detecting a collision, the device can retain the transferred data and issue a service request to the host computer. The detection method of the present invention does not need a waiting period before a collision is detected. If the bus is occupied by other devices, the device will terminate its data transmission. In addition, this detection method is also useful for locating multiple devices with the same hardware jumper address, such as the mouse scaler 11 and 12.

In this case, the host computer can change the address of the device by making the colliding devices share the same address, and the host computer selects these devices by saying the R3 command to achieve the above purpose. As shown in FIG. 3 , the register 322 (one of registers of the device) contains the following information. Bits A0 to A731 are the processing program information of the device, from which the host computer can know the function of the device and the purpose of the data provided by the device. A8 to A11 32 is the address segment, when more than one device coupled to the bus has the same command address, the content of this segment is changed. At this time, one of the soft address segments will be assigned to A8 to A11 32 bits, which will be used as the command address of the device later. Previously, these bits contained a random number to aid in collision detection. For example, if two mice receive a Speak command from R3 and start to execute the Speak command at the same time, neither will detect a collision. But if the address segment 32 of the register R3 22 is a random number, the final output of the two devices will be different. At this time, one of the two devices will detect the collision and stop executing the said command. A12 34 bits It is a high-speed enable bit. If this bit is set, the data transmission adopts a higher modulation rate (50 microseconds per bit frame). The high-speed enable bit is set by the host computer. If the host computer cannot receive data at a high modulation rate with the high-speed enable bits, it sets the high-speed enable bits of all devices low. If the host computer can receive data at a high modulation rate and the device can transmit at a high modulation rate (that information is contained in register 3 in handler bit 31), the host computer sets the high speed enable bit 32 of the device high. As mentioned earlier, bit A13 35 is a service request enable bit, which is set by the host computer so that the device can perform service request processing. A14 36 and A15 31 bits are reserved for future use and are set to 0. After receiving the say R3 command, the device provides its state (that is, the address of the handler) to the host computer. If the bus couples two devices of the same type, only one will respond to commands because the other will detect a collision. Figure 2 shows the method of assigning new addresses on the bus.

After receiving the say R3 command (shown as box 10 in Figure 5), the device will send out its status from register 3. If the data line turns to low level, the device thinks that a collision has occurred (as shown in branch 104 in Figure 5), stops sending (that is, stops executing the command), and sets its internal flag to indicate that a collision has occurred (such as shown in block 106 of Figure 5). The host computer sends a listen R3 command (shown in block 107 of Figure 5) to the address of the mouse pointer. Each command resets the internal collision flag of the device, and the device checks whether its collision bit is set (as shown in box 108 in Figure 5), and if it is not set (as shown in box 109 in Figure 5), the device will use The soft address in the Listen 3 command replaces bits A8 to A11 (shown in block 111 of FIG. 5). In this way, the new address of the device can be tracked by the host computer and the address of the device receiving the command can be changed. If the device detects a collision bit after listening to the R3 command (as shown in block 110 of Figure 5), the device does not change the soft address bits, but may change other segments of R3. The host computer issues another R3 command to check if any device still uses the mouse address. At this point, the remaining mouse scaler will send out its start bit (as shown in block 102 of FIG. 5), detect no collision, and send out its status from register 3 (as shown in 105a-105b of FIG. 5). Show). The host computer sends back a listen R3 command to the mouse address (as shown in block 107 of Figure 5). At this point, the remaining mouse scalers will not detect To the collision bit that is set in this example (as shown in branch 109 of Figure 5), then replace the A8 to A11 bits in register 3 with the soft address received from the host computer (as shown in frame 111 of Figure 5 ). The host computer then sends another R3 command to the mouse (as shown in block 101 of Figure 5), at which point, because there is no mouse at that address, the time will be exceeded on the bus, and the host computer knows Each device that shares the mouse address has been assigned a new address.

In one embodiment of the present invention, there is a device on the external device for indicating validity, called a validity indicator. The validity indicator can be a special key on the keyboard or a button on the mouse cursor. When more than one device is coupled to the bus, the host computer can display a message requesting that a device use an availability indicator. Then, the host computer listens to the R3 command, which changes the address of the active device. In this way, each device can be located and assigned a new address in a multi-user system.

Up to this point, the peripheral bus that allows multiple peripheral devices to be coupled to a host computer through a single port has been fully described.

Claims (5)

1. A method for transmitting signals and data between a host computer, a first external device, and a second external device, wherein the first and second external devices are connected to the host computer through a bus; wherein, the host computer, The transmission of signals and data between the first external device and the second external device is carried out under the control of the host computer through the bus; wherein, the first and the second external device have a same first address; wherein, the first and the second external device have the same first address; The second external device is in an off state initially; It is characterized in that the method comprises the steps of: (A) the host computer specifies a first extended address to the first external device, wherein the first extended address is unique to the first external device; (B) the host computer specifies a second extended address to the second external device, wherein the second extended address is unique to the second external device; (C) If the host computer is to transmit signals and data to the first external device and direct the first external device, then (i) sending a first address from the host computer to said bus, wherein the first address addresses the first and second external devices, wherein, when the first and second external devices are addressed by the first address, hold Disabled; (ii) activate the first external device by sending the first extended address from the host computer to the first external device via the bus, wherein the first external device is activated only after receiving the first extended address, wherein the second external device the device remains switched off; (ⅲ) After the first external device is activated by the first extended address, the host computer only uses the first address to address the first external device to send signals and data to the first external device, wherein, after the first external device is activated , the host computer does not need to send the first extended address to address the first external device, wherein the second external device remains closed; (D) When the first external device is activated, if the host computer is to transmit signals and data to the second external device and address the second external device, then (i) by sending a second extended address via the bus from the host computer to an unactivated second external device, wherein the second external device is activated only after receiving the second extended address, wherein when the second external device is activated When the second extended address is activated, the first external device is deactivated; and (ii) After the second external device is activated by the second extended address, the host computer only uses the first address to address the second external device to send signals and data to the second external device, wherein the second external device is activated Afterwards, the host computer does not need to send the second extended address to address the second external device, wherein the first external device remains turned off. 2. The method according to claim 1, further comprising a third external device connected to the bus and a fourth external device connected to the bus, wherein the third and fourth external devices have the same second address, Wherein, the third and fourth external devices are also in the closed state initially, wherein the host computer assigns a unique third extended address to the third external device, wherein the host computer assigns a unique fourth extended address to the fourth external device . 3. The method according to claim 2, characterized in that said method further comprises the steps of: (E) When the second external device is activated, if the host computer addresses the third external device to transmit signals and data to the third external device, then (i) sending a second address from the host computer to the bus, wherein the second address addresses the third and fourth peripheral devices, wherein the third and fourth peripheral devices remain off while the second address is addressing; (ii) The host computer activates the third external device by sending the third extended address to the third external device via the bus, wherein the third external device is activated only after receiving the third extended address. Wherein, the fourth external device remains in an off state, wherein, when the third external device is activated by the third extended address, the second external device is deactivated; (iii) After the third external device is activated by the third extended address, the host computer only addresses the third external device with the second address to send signals and data to the third external device, wherein, after the third external device is activated Afterwards, the host computer addresses the third external device without sending the third extended address, wherein the fourth external device remains turned off. 4. The method of claim 3, wherein at least one of the first, second, third and fourth external devices has a meter. 5. The method of claim 3, wherein at least one of the first, second, third and fourth peripheral devices has a system protection device.

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