Toshiba TLCS-900/L1 Series Manual page 20

(2) Protection of register contents
(Purpose)
An item for mistake operation by inputted noise.
To execute the program certainty which is occurred mistake operation, the
protect-register can be disabled write operation for the specific SFR.
Write disabled SFRs
1. CS/WAIT controller
B0CS, B1CS, B2CS, B3CS, BEXCS,
MSAR0, MSAR1, MSAR2, MSAR3,
MAMR0, MAMR1, MAMR2, MAMR3
2. Clock gear (only EMCCR1 can be written to.)
SYSCR0, SYSCR1, SYSCR2, EMCCR0
(Block diagram)
To EMCCR1
Write value other than 1FH
(Setting method)
Writing any value other than 1FH to the EMCCR1 register turns on protection,
thereby preventing the CPU from writing to the specific SFR.
Writing 1FH to EMCCR1 turns off protection.
The protection status is set in EMCCR0<PROTECT>.
Resetting initializes the protection status to off.
Protect register
EMCCR0<PROTECT>
S Q
Write 1FH
R
Write signal SFR
91C829-18
TMP91C829
Write signal to the disabled SFR
Write signal to the other SFR
2006-03-15