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User’s Manual U11969EJ3V0UM00
79
CHAPTER 3 CPU FUNCTIONS
(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.
Bit Position
Bit Name
Function
4
PRERR
Protection Error Flag
Indicates that writing to a special register has not be executed in the correct sequence, and
protection error occurred.
Accumulate flag
0 : Protection error does not occur.
1 : Protection error occurs.
0
UNLOCK
Unlock Status Flag
Read-only flag. Indicates the PLL unlock state. (For details, refer to 6.4 PLL Stabilization.)
0 : Locked
1 : Unlocked
Operation conditions of PRERR Flag
• Set conditions:
(1) If the store instruction most recently executed to peripheral I/O does not write
(PRERR = “1”)
data to the PRCMD register, but to the specific register.
(2) If the first store instruction executed after the write operation to the
PRCMD register is to a peripheral I/O register other than the specific registers.
• Reset conditions:
(1) When “0” is written to the PRERR flag of the SYS register.
(PRERR = “0”)
(2) At system reset.
Address
FFFFF078H
7
0
SYS
6
0
5
0
4
PRERR
3
0
2
0
1
0
0
UNLOCK
After reset
0000000XB
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