JP3042266B2 - Memory access method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory access method.

[0002]

2. Description of the Related Art Conventionally, a programmable logic controller (hereinafter, referred to as PLC) for controlling equipment in a factory has a microprocessor unit (hereinafter, referred to as MPU).
It is described. ) And random access memory (hereinafter RA)
Described as M. ) And so on. When accessing data in the RAM in the PLC, the built-in MPU performs a process as shown in the flowchart of FIG.

First, a record pointer A for storing data at a desired memory address and a number B of records in a bank, which is the maximum number of records per bank, are read from a register temporarily stored in the MPU (S20). ). The record pointer A is divided by the number of records B in the bank, and the quotient obtained by the division is set as the bank value C and the remainder is set as the offset value D (S21). The bank value C is added to the bank offset E to obtain the bank F (S22). The address J is obtained by multiplying the offset value D by the record size G, which is the maximum number of bytes set for one record, and further adding the record offset E (S23).

The address of a desired memory is determined from the bank F and the address J calculated as described above, and the memory is accessed according to the determined address.

[0005]

Generally, the MPU also has a division function among the operation functions. However, the division requires more processing steps than the addition and multiplication, so that the processing speed is reduced. This delay in processing speed is a delay time when calculating addresses of necessary data.

Therefore, when calculating the target address by dividing the register, there is no problem if the MPU in the PLC is an MPU capable of high-speed processing. In the generally used MPU, as a result, the memory access time becomes long, and a problem has arisen in a large amount of memory access or high-speed memory access.

It is an object of the present invention to reduce the load on the memory access of the MPU, and to reduce the
An object of the present invention is to provide a memory access method that enables a large amount of memory access or high-speed memory access even if U is used.

[0008]

SUMMARY OF THE INVENTION The present invention for achieving the above object comprises a bank for dividing a storage area into a plurality of parts, and a record for further dividing the bank into a plurality of parts. A memory access method for accessing a logical ring buffer memory in which data is sequentially stored in the bank, and stored again from the beginning when the data is stored until the end of the bank. depending on the data
The record pointer configured Te provided, the Rekodopo
The data of the interface is shifted by a predetermined bit and the bank value is
And add the bank offset to this bank value
Then, the data of the record pointer is
Use an offset mask to set the offset value,
Multiply the offset value by the record size and multiply the resulting value by
Add the record offset to find the address,
The logical ring buffer memory according to the
It is characterized by accessing a memory .

[0009]

According to the memory access method of the present invention, data of a bank and a record, which are addresses of a logical ring buffer memory, are stored in a record pointer, and a desired logical ring buffer memory address is determined from the record pointer to perform memory access.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A memory access method according to the present invention will be described below with reference to the accompanying drawings.

According to the memory access method of the present invention, a logical ring buffer memory composed of a record obtained by further dividing one bank of a plurality of banks and a record pointer in which data of the bank and the record are written are processed. Thus, the address is determined.

For example, as shown in FIG.
The record pointer stored in 1 is composed of 8 bits. The 0th to 5th bits are assigned offset parameters which are address data, and the 6th to 7th bits are assigned bank parameters which are bank data. I have. Next, the MPU 1 which performs data processing shifts the record pointer by 6 bits to obtain a bank value, writes the bank value to the 8-bit adder 5 and adds it to the bank offset. Is written to the bank selector 6 which selects the 0th and 1st bits as a bank and selects the bank of the RAM 4 which is a logical ring buffer memory.

On the other hand, the above-mentioned record pointer is MPU1
And is used as an offset value. This offset value is multiplied by the record size, which is the maximum number of bytes set in one record, by an 8-bit shift register,
Further, the data is added to the record offset by the 8-bit adder 3 to be an address of the RAM 4.

Processing the record pointer as described above,
A bank and a record are obtained, and a desired address of the logical buffer memory can be accessed.

Note that the logical ring buffer memory R
The concept of the storage area of AM4 is 0 to 3 as shown in FIG.
Are divided into four banks, and this one bank is further divided into records between addresses 00H to FFH. The RAM 4 divided by such a concept is shown in FIG.
As shown in (b), data is read or written sequentially from bank 0 to bank 3 in the rotation direction. When data is written to bank 3, data is written again from bank 0.

The reading of the data is performed by eight reading pointers R0 to R8, and the writing of the data is performed by the writing pointer W.

FIG. 3 is a flowchart of control for obtaining a bank and an address from a record pointer. That is, the record pointer A is read (S10), the record pointer A is shifted right by 6 bits, and the shifted value is set as the bank value C (S11). Also, the record pointer is masked with an offset mask M to obtain an offset value D (S12). Next, this bank value C
Adds the bank offset E to obtain the bank F (S1
3). The address J is obtained by multiplying the offset value D by the record size G, which is the maximum number of bytes set for one record, and further adding the record offset E (S14).

By operating as described above, the memory access method of the present invention determines the address of the desired logical ring buffer memory from the bank and record data stored in the record pointer and performs memory access. The load related to access can be reduced.

[0019]

As described above, according to the present invention,
Since the load on the memory access of the MPU can be reduced, a large amount of memory access or high-speed memory access can be performed.

[Brief description of the drawings]

FIG. 1 is an embodiment of a circuit for operating a memory access method of the present invention.

FIG. 2 is a diagram for explaining a logical ring buffer memory.

FIG. 3 is a flowchart illustrating control of a memory access method according to the present invention.

FIG. 4 is a flowchart illustrating control of a conventional memory access method.

[Explanation of symbols]

1 ... MPU, 2 ... 8-bit shift register, 3, 5 ... 8-bit adder,
4 ... RAM, 6 ... Bank selector.

Claims (1)

(57) [Claims] 1. A bank for dividing a storage area into a plurality of parts, and a record for further dividing the bank into a plurality of parts. Data input / output to / from the banks are sequentially stored in the banks, and stored until the end of the banks. A memory access method for accessing the logical ring buffer memory that stores the data sequentially from the beginning when it is executed, further comprising: providing a record pointer constituted by bank and record data which are addresses of the logical ring buffer memory; Is shifted by a predetermined bit
The bank value, and add the bank offset to this bank value.
Then, the bank is obtained, and then the data of the record pointer is shifted to a desired offset.
The offset value by masking with the offset mask.
Value is multiplied by the record size, and the resulting value is
An address is obtained by adding an offset, and the logical ring buffer is obtained based on the obtained bank and address.
Memory access method characterized by accessing Famemori.