Common Register Bank Prefix (Cmr) - Fujitsu MB90460 Series Hardware Manual

CHAPTER 3 CPU
3.9.2

Common Register Bank Prefix (CMR)

The common register bank (CMR) prefix is placed before an instruction that accesses a
register bank to change the register accessed by the instruction to the common bank
(register bank selected when RP = 0) at 000180
register bank pointer (RP) value.
■ Common register bank prefix (CMR)
To facilitate data exchange between multiple tasks, a relatively simple means of accessing a fixed register
bank regardless of the current register bank pointer (RP) value is necessary. This is the reason that the
2
F MC-16LX provides a common register bank for tasks, which is called the common bank. The common
bank is located at address 000180
If the common register bank prefix (CMR) is placed before an instruction that accesses a register bank,
registers accessed by the instruction can be changed to the common bank (register bank selected when RP =
0) at 000180
Note that caution is required when this prefix is used with the instructions listed in Table 3.9-4.
Table 3.9-4 Instructions whose use requires Caution when the Common Register Bank Prefix (CMR) is
used
Instruction type
String
instruction
Flag change instruction
PS return instruction
ILM setting instruction
60
to 00018F
H
to 00018F regardless of the current register bank pointer (RP) value.
H H
Instruction
MOVS
SCEQ
FILS
AND CCR, #imm8
POPW PS
MOV ILM, #imm8
to 00018F regardless of the current
H H
.
H
MOVSW
Do not place the CMR prefix before the
SCWEQ
string instruction.
FILSW
The effect of the prefix extends to the
OR CCR, #imm8
next instruction.
The effect of the prefix extends to the
next instruction.
The effect of the prefix extends to the
next instruction.
Explanation