
36
μ
PD70433
3.6
REGISTER FILE SPACE
The register file space is shown in Figure 3-5.
The size of the register file space is 512 bytes, and a maximum 16-bank register set can be set.
The register file space is separate from the memory space, and in addition to accesses using a register manipulation
instruction as with the V25 and V35, the register file space can be accessed as data memory by adding a special prefix
instruction (IRAM:) to a memory manipulation instruction. (Access is performed asynchronously independently of the
external bus cycle.
When the IRAM: prefix instruction is added to a memory manipulation instruction, the CPU performs a data access with
the low–order 9 bits of the memory address offset value as the register file address. In this case, segment register and
physical address addition is not performed, and an external bus cycle is not initiated.
Example
Label1: MOV
IRAM : [0024H], AW..... <1>
[0056H], BW
MOV
..... <2>
<1> This shows the case where data is transferred to the register file space using an "IRAM:" prefix
instruction. The AW register value is stored in address 24H of the register file.
<2> This shows the case where an instruction for data transfer to the memory space is used.
If the IRAM prefix instruction is added to the primitive block transfer instruction and BCD operation instruction, which
specify the source block and destination block, it becomes effective for the destination block.
Also, the macro service conrol word area (008H to 03FH), the macro service work area (000H to 007H), and the area
used by the macro service channel (008H to 0FFH) are allocated in overlapping fashion in the file space. If a specific macro
service which requires work area (RTOPTRN) is not used, these work areas can be used as data space.