JPS6249680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a write margin measuring device for a user-writable read-only memory (hereinafter referred to as PROM).

Conventionally, PROMs have the convenience of being writable by the user, but have had the following problems with their reliability.

In other words, PROM may have insufficient margin for setting the write conditions (write margin) due to fluctuations in its manufacturing conditions, etc., so when writing the desired program using a writer, it is important to set the write conditions appropriately. Otherwise, there was a fear that reliable writing would be performed only after several writings, or that no writing would be performed at all.

Therefore, PROMs with such a small write margin often have poor information storage characteristics, and if they are used for a long period of time, there is a risk that the written contents such as programs and data may change. This could even cause a system failure of the system in which it is used.

Although it is extremely important to reliably write programs, data, etc. to PROM, there has been no means to easily measure the write margin or write characteristics. Since the user could not easily and reliably know the write margin, a great deal of effort was required to check it, and sufficient reliability could not be obtained.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, improve the efficiency of PROM writing, and
It is an object of the present invention to provide a write margin measuring device for obtaining reliability by eliminating in advance those with insufficient write margin.

The features of the present invention include a writing means capable of writing to the writable read-only memory to be measured under specified write conditions, and a write means capable of writing to the writable read-only memory to be measured; write condition variable setting means capable of dividing all addresses into a plurality of blocks and specifying any write condition below the rated write condition according to the number of blocks;
Each write condition, such as the voltage, current, width, and rise time of the write pulse, was gradually changed from weaker than the rated write condition to the rated write condition, and A display and display system that can write to divided blocks, collate the write results for each block, calculate the write rate for each block, and display or record the write margin and other necessary results calculated from the write rate for each block. The present invention provides a write margin measuring device including a recording means and a control/processing means capable of performing necessary control/processing related to each of these means.

In addition, to explain this in detail, the write conditions, that is, the voltage, current, width, rise time, etc. of the write pulse, are gradually changed from weaker than the rated write condition to the rated write condition, and each It is possible to measure the write margin by writing to divided blocks of the measurement PROM, comparing the write results for each block, and determining whether sufficient writing has been performed under any of the write conditions. It is something.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an embodiment of a write margin measuring device according to the present invention, and FIG. 2 is a flowchart thereof.

Here, 10 is a write margin measuring device, 1
1 is a processing unit (MPU) related to control/processing means;
12 is the internal memory (RAM), 13 is the input/output control circuit (IOC), 14 is a pulse generator (PG) related to the writing means, and 15 is a keyboard (KBD) related to the writing condition variable setting means. , 16 is a display (CRT) related to display/recording means, 20
is the PROM to be measured.

First, before measuring the write margin, the PROM
20 (for example, fuse-cut type) is divided into a plurality of blocks as appropriate, each write condition corresponding to the number of divisions is set, and the data is stored in the internal memory 12. (Steps in Figure 2).

This write condition data includes, for example, weak write,
Depending on medium writing and rated writing, the keyboard 1
5, is stored in the internal memory 12 via the input/output control circuit 13 and the processing device 11.

Note that the address designation at which the PROM 20 should be written is randomly determined by the processing device 11 according to random numbers, and the address is stored in the internal memory 12.

Further, the measuring device 10 is controlled by the processing device 11 according to a predetermined program stored in the internal memory 12 in advance.

Next, when a predetermined operation is performed on the keyboard 15 (eg, operation of a measurement start button) to start a measurement operation, the measurement operation of the apparatus is started (step).

This activation operation is not necessarily necessary, and activation may be performed automatically upon completion of the above steps.

As a result, the processing device 11 first reads data from all addresses of the PROM 20 via the input/output control circuit 13, and checks (blank check) whether or not all addresses are unwritten (step 1). ).

As a result, if there is an address that has been written, necessary items such as the address and data are displayed on the display 16 so that the PROM 20 can be replaced with another one or write and erase operations can be performed (step). .

If all addresses have not been written, the predetermined write conditions and write addresses are sequentially retrieved from the internal memory 12 for each divided block and sent to the pulse generator 14 via the input/output control circuit 13.
, and write to the PROM 20 under predetermined conditions (step).

When the write operation is completed, the processing device 11
For each block of the PROM 20, the write data for each address is sequentially read, compared with the data related to the address stored in the internal memory 12, and the write rate (for example, the number of addresses to which writing should be performed) is , ratio of the number of addresses to which writing is actually being performed) and other necessary data are calculated (step).

Next, the verification results (including the value of the write margin, which will be described later) are displayed on the display 16 for each block, and the measurement operation is completed (step).

As a result of the above, the write rate can be determined for each block of the PROM 20. For example, the difference in burnout voltage, pulse width, etc. when the write rate becomes 100% under the rated write condition and the write condition below the rated condition is calculated as the write margin. It can be determined as a value.

Although the PROM 20 to be measured has been described above as a fuse-burning type, the pulse generator 14 that performs writing should be of an appropriate writing type even if it is of the other type such as a joint destruction type or an ultraviolet erasing type. The write margin can be measured in the same way.

As described above in detail, according to the present invention, it is possible to realize a device that can arbitrarily and systematically vary and measure the write margin of PROM, so that it is possible to perform memory screening or know the optimum write conditions. This makes it possible to reliably write programs with good information storage retention characteristics, which in turn has a significant effect on improving the reliability of systems using the memory.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a write margin measuring device according to the present invention, and FIG. 2 is a flowchart thereof. 10...Write margin measuring device, 11...Processing device, 12...Internal memory, 13...I/O control circuit,
14...Pulse generator, 15...Keyboard, 16...
Display, 20...PROM.

Claims (1)

[Claims] 1. A writing means capable of writing to the writable read-only memory to be measured under specified write conditions, and a plurality of addresses for part or all of the writable read-only memory to be measured. A write condition variable setting means that can divide the program into blocks and specify any write condition below the rated write condition according to the number of blocks, and write conditions such as the voltage, current, width, and rise time of the write pulse can be set according to the rated write condition. Gradually change the write conditions from weaker to rated write conditions, write to the divided blocks of the above-mentioned writable read-only memory under test, compare the write results for each block, and write to each block. A display/recording means capable of calculating the write rate for each block and displaying or recording the write margin calculated from the write rate for each block and other necessary results, and a control/recording means capable of performing necessary control/processing related to each of these means. 1. A write margin measuring device comprising a processing means.