JPS61235953A - One chip microcomputer - Google Patents

Abstract

PURPOSE:To shorten the test time, and to obtain a high reliability by providing a test use electrode on a programmable ROM, and executing independently its test through this electrode. CONSTITUTION:A CPU, an input/output circuit I/O, a timer circuit TM, also a RAM, and a EPROM are provided on a semiconductor substrate, and bonding pads P which are coupled to a power source terminal, an input terminal, an output terminal, and various control terminals, etc. are placed in the peripheral part of the semiconductor substrate. In addition to these bonding pads P, a test use electrode (pad) TP is provided in the peripheral part of the EPROM. In this way, various tests of the EPROM can be executed efficiently in a short time through this pad.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a one-chip microcomputer, such as an EF microcomputer with a built-in ROM (read-only memory) in which a program for information processing is stored.
The present invention relates to a technique that is effective for use in devices configured with ROM.

[Background technology]

In a 1-chip micro combinator, the built-in R
It performs predetermined information processing according to a program written in the OM. Prior to this invention, the inventors of the present application had developed an EPROM (Electrically Programmable Read Only Memory) as the built-in ROM.
I thought of using . By using EPROM in this manner, it is possible to quickly provide a one-chip microcomputer with the information processing function desired by the user, and it is possible to improve mass productivity. That is, if a mask-type ROM is used as the built-in ROM, time is consumed in manufacturing various masks for writing programs therein and in manufacturing the masks.

However, when an EPROM is used as described above, testing thereof requires a long time. That is,
Operation test of the microcomputer itself and the above EPRO
In order to check whether the program has been written to M intermittently throughout the execution of the program, a huge number of test steps are required. In addition, for each microprocessor operation test, EPROM write/read program execution), it is necessary to connect the same bonding pad (input terminal/output terminal) two or three times to the surface of the same bonding pad (input terminal/output terminal). It is necessary to crimp the probe. This causes multiple scratches on the surface of the bonding pad.
It has been found that this causes a problem of reduced bondability during the assembly process.

Regarding EPROM, for example, Japanese Patent Application Laid-open No. 54-15
See No. 2933, and regarding a 1-chip microcomputer using an external EFROM, see, for example, page 566 of ``Hitachi Microcomputer Data Book/8-bit Single Chip 1'' published by Hitachi, September 1988.

[Purpose of the invention]

An object of the present invention is to provide a one-chip microcomputer that has a simple configuration, reduces test time, and has high reliability.

The above and other objects and novel features of this invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, test electrodes are provided in the built-in programmable ROM in which information processing programs are stored by electrical writing, and the test can be performed independently through the electrodes.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of a one-chip microcomputer to which the present invention is applied.

In the figure, the part surrounded by dotted lines is an integrated circuit LSI, and each circuit block formed here constitutes a one-chip microcomputer as a whole, and is made of silicon using known semiconductor integrated circuit manufacturing technology. Like 1
formed on a single semiconductor substrate.

The symbol CPU is a microprocessor, and its main constituent blocks are exemplarily shown as a representative.

A is achiemulator, X is index register, CC
is the condition code register, SP is the stack pointer, PCH and PCL are the program counters, and CPU-
C0NT is a CPU controller, and ALU is an arithmetic and logic operation unit.

The configuration of such a microprocessor CPU is described, for example, in ■r published by Ohmsha on April 10, 1978.
Since this is well known from Microcomputer Fundamentals by J. Mitsuharu Yada, a detailed explanation thereof will be omitted.

The symbol I10 is an input/output port,
It contains a data transmission direction register therein. Also, what is indicated by the symbol I is an input-only port.

What is indicated by the symbol O8C is an oscillation circuit, which forms a highly accurate reference frequency signal using an external crystal resonator Xtal, although it is not particularly limited. This reference frequency signal forms the clock pulses required in the microprocessor CPU. Further, the reference frequency signal is also used as a reference time pulse of a timer.

This timer consists of counter C0UT, prescaler PR
and a controller C0NT.

The symbol RAM is a random access
It is a memory and is mainly used as a temporary data storage circuit.

What is indicated by the symbol EPROM is an electrically programmable read-only memory, into which programs for various information processing are written.

The above circuit blocks are connected to each other by a bus BUS, with the microprocessor CPU as the center. This bus BUS includes a data bus and an address bus. Note that the bus BUS is connected to the external terminal ADD.
is combined with

In the microcomputer of this embodiment, the above E
Since FROM is used, a control circuit WCON for writing and the like is provided. This control circuit WCON identifies the voltage level supplied from the external terminal Vl)G) and
Control of the write/read operation mode and supply the write high voltage to the EFROM. Once supplied,
The read operation mode is entered when the EPROM is selected by the CPU. On the other hand, from the external terminal vpp to the EPROM
When a high voltage for writing (for example, about 12 V) is supplied, the data cover of the EFROM is put into operation, and according to the information supplied from the data bus, the data bus is formed using the high voltage vpp. A logic “0” write signal is processed and written to the selected memory cell (FA
Logic "O" is written to MO3) transistor). Note that at this time, addressing of the EFROM is performed by an address signal supplied from an external terminal.

FIG. 2 shows a schematic layout diagram of an embodiment of the one-chip microcomputer described above.

In the same figure, on the semiconductor substrate (LSI) there are a microprocessor CPU, an input/output circuit I10, an oscillation circuit OSC shown in FIG. It consists of a timer circuit TM consisting of a C0UT, a prescaler PR, a controller C0NT, etc., a RAM, and an EOROM indicated by a solid line. Power supply terminals and input terminals are located around the semiconductor substrate.

A bonding pad P coupled to an output terminal, various control terminals, etc. is arranged. These pounding pads P
Separately, electrodes (pads) TP for testing are provided around the EPROM.

Note that this pad TP may be arranged side by side with the bonding pad if there is extra space around the semiconductor substrate.

Note that the test pads are used only when testing a one-chip microcomputer completed on a semiconductor wafer, and are not connected to external terminals.

In various tests of the one-chip microcomputer of this embodiment, the above-mentioned bonding pad P is used to perform DC tests, functional tests, etc. of the microprocessor CPU, etc. On the other hand, in EPROM testing, tests such as writing/reading of the EFROM are performed independently by a memory tester using the above-mentioned test pads. With such a simple configuration in which test pads are provided for the EPROM, various tests on the EFROM can be directly performed in a short time.

〔effect〕

(1) By providing a test pad in the built-in programmable ROM that stores information processing programs, the effect is that various tests of the E F ROM can be performed efficiently in a short time via this band. It will be done.

(2) According to the above (1), it is possible to evaluate the EPROM with higher accuracy, so that the reliability can be improved.

(3) Since the pads used for testing the microprocessor and the like are different from the pads used for testing the EFROM, scratches on the surface of the bonding pads connected to external terminals can be minimized. This makes it possible to prevent deterioration in bondability during the assembly process, and in combination with the above (2), it is possible to achieve the effect that reliability can be further improved.

(4) According to (1) above, since the number of pads for testing an EFROM individually is relatively small, it is possible to simultaneously perform probing on, for example, multiple chips of EFROM. As a result, it is possible to test multiple chips of EPROM in parallel, thereby achieving the effect that the test time can be further shortened.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that this invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, the programmable ROM may be an EEPROM that can be electrically erased instead of an EFROM. Further, a one-chip microcomputer may be equipped with, for example, an A/D conversion circuit, depending on its functions.

[Application field]

The present invention can be widely used in single-chip microcomputers incorporating a programmable ROM that can be electrically written.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a one-chip microcomputer to which the present invention is applied, and FIG. 2 is a schematic layout diagram thereof.

Claims (1)

[Scope of Claims] 1. A one-chip microcomputer characterized by having a built-in programmable ROM that can be electrically written to and electrodes for testing the programmable ROM. 2. The one-chip microcomputer according to claim 1, wherein the programmable ROM is an EPROM.