JPH0346920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for writing/reading data to/from a RAM, and particularly relates to a method for inspecting a RAM.

Recent office automation (OA) equipment has come to have a built-in microprocessor and store and process data in RAM. In order to reduce costs, these OA devices use RAM.
Also, many write/read circuits do not have error detection means.

However, as the performance of office automation equipment increases, the amount of data processed increases, and so does the capacity of RAM. Therefore, the reliability of RAM functionality has become more important. Therefore, many of these devices check the RAM function when the power is turned on or when the operator diagnoses the device.

When checking the RAM function, it is necessary to be able to easily perform a reliable function check including the write/read circuit.

[Conventional technology]

To check the RAM function, first write data [55H] to a certain address, then read it to see if it has actually been written, then write data [AAH] to the same address, and then read it. Check. This operation is generally performed for all address spaces.

That is, by writing and reading 010101 and then writing and reading 101010 to the same address, RAM abnormality detection is performed based on whether an error has occurred in the data.

[Problem that the invention seeks to solve]

If you check the RAM function using the above method, for example, the check result may be good even though the RAM decoding circuit has failed and the address signal is not output correctly and no data is written to the specified address. It may happen.

In other words, the least significant bit of the address signal is always “1”
If this happens, data will be written to address [XXX1] regardless of whether address [XXXX0] or [XXXX1] is specified. However, since the above method does not check the address, there is a problem in that the fault is not detected and the fault is returned.

[Means for solving problems]

The above problem is that in a device that writes and reads data to and from RAM, the first step is to write specific data A to all addresses of RAM;
a second step of specifying the first address to read the data and confirming whether the data is the specific data A; and when the specific data A is confirmed, specifying the address and reading the data; writes a different specific data B, then specifies the address, reads the data, and confirms whether the data is the specific data B, and when the specific data B is confirmed, the a fourth step of reading data by sequentially specifying only addresses larger than the address, and checking whether the data is the specific data A, and sequentially adding 1 to the first address to read out the data, and sequentially adding 1 to the first address to read the data. This problem is solved by a RAM inspection method according to the present invention, in which the second to fourth steps are performed on an address.

[Effect]

In other words, data is written/written for each address of RAM.
At the same time as reading, it is detected whether data at other addresses has been destroyed.

〔Example〕

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention, showing an example of a printer circuit, and FIG. 2 is a flowchart explaining the operation of FIG. 1.

The microprocessor 1 reads a program stored in the ROM 2 and operates. Print data and the like are input from the interface control circuit 4. The microprocessor 1 stores the print data in the RAM 3.
write to.

The print data written in the RAM 3 is read out by the microprocessor 1, and if it is a character code, the corresponding character pattern is read out from the character generation circuit 7 and sent to the print head control circuit 10. The character pattern sent to the print head control circuit 10 is printed by the print head 11.

At this time, the microprocessor 1 simultaneously controls the space control circuit 8 to drive the space motor 9 to cause the carriage carrying the print head 11 to perform a space motion.

If the print data read from the RAM 3 includes a line feed specification, the microprocessor 1 outputs a line feed control circuit 5.
is controlled to drive the line feed motor 6 to feed the paper.

From the operator panel 13 to the microprocessor 1 via the input port 12, as shown in FIG.
When the microprocessor 1 receives an instruction to start a write/read test of the RAM 3, the microprocessor 1 reads a program from the ROM 2 and starts checking the RAM 3.

First, write specific data such as hexadecimal [55H] to all addresses in RAM3. After that, specify the first address and try reading the data. If the read data is [55H], it is determined that RAM3 is abnormal, but if the read data is [55H], another specific data, for example 16, is stored at the same address.
Write [AAH] in decimal.

Try reading the data by specifying the address where [AAH] was written above. If the read data is [AAH], it is determined that the RAM 3 is abnormal, but if the read data is [AAH], data is read by sequentially specifying only addresses larger than the first address.

If the data is not [55H]
If there is an error in RAM3 or if the content of the address after the first address becomes AAH, it is determined that it is a failure of the decoding circuit, but if all the read data remains [55H], then the first address is sequentially incremented by 1 and the above operation is repeated within the address of RAM3, and when the address of RAM3 is exceeded, RAM3 is determined to be normal and the process ends.

〔Effect of the invention〕

As explained above, the present invention can easily check all RAM functions including the write/read circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention, and FIG. 2 is a flow chart explaining the operation of FIG. 1 is microprocessor, 2 is ROM, 3 is
RAM, 4 is an interface control circuit, 5 is a line feed control circuit, 6 is a line feed motor, 7 is a character generation circuit,
8 is a space control circuit, 9 is a space motor, 1
0 is the print head control circuit, 11 is the print head, 1
2 is an input port, and 13 is an operator panel.

Claims (1)

[Claims] 1 In a device that writes and reads data to and from RAM, the first step is to write specific data A to all addresses in RAM, read the data by specifying the first address, and confirm that the data is specified. The second step is to confirm whether the data is A, and when specific data A is confirmed, specify the address and write specific data B, which is different from data A, and then specify the address and write the data The third step is to read out the data and check whether the data is specific data B, and when the specific data B is confirmed, read out the data by sequentially specifying only addresses larger than the above address, and confirm that the data is specific data B. and a fourth step of checking whether the data is data A, and sequentially adding 1 to the first address and performing the second to fourth steps for all remaining addresses in the RAM. RAM inspection method.