CHAPTER 3 CPU FUNCTIONS
User’s Manual U13850EJ4V0UM
105
(1) Command register (PRCMD)
The command register (PRCMD) is a register used when write-accessing the specific register to prevent incorrect
writing to the specific registers due to the erroneous program execution.
This register can be written in 8-bit units. It becomes undefined values in a read cycle.
Occurrence of illegal store operations can be checked by the PRERR bit of the SYS register.
Figure 3-25. Command Register (PRCMD)
After reset: Undefined W
Address: FFFFF170H
Symbol
7
6
5
4
3
2
1
0
PRCMD
REG7
REG6
REG5
REG4
REG3
REG2
REG1
REG0
REGn
Registration code
0/1
Any 8-bit data
(2) System status register (SYS)
This register is allocated with status flags showing the operating state of the entire system. This register can be
read/written in 8- or 1-bit units.
Figure 3-26. System Status Register (SYS)
After reset: 00H
R/W
Address: FFFFF078H
Symbol
7
6
5
<4>
3
2
1
0
SYS
0
0
0
PRERR
0
0
0
0
PRERR
Detection of protection error
0
Protection error does not occur
1
Protection error occurs
Operation conditions of PRERR flag are shown as follows.
(a) Set conditions (PRERR = 1)
(1) When a write operation to the specific register took place in a state where the store instruction operation
for the recent peripheral I/O was not a write operation to the PRCMD register.
(2) When the first store instruction operation following a write operation to the PRCMD register is to any
peripheral I/O register apart from specific registers.
(b) Reset conditions: (PRERR = 0)
(1) When 0 is written to the PRERR flag of the SYS register.
(2) At system reset.
Содержание MPD703030A
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