Motorola MPC533 Reference Manual page 303

not entered before power disconnect, there is a chance of data loss in these registers. To
minimize the possibility of data loss, the MPC533 includes a key mechanism that ensures
data retention as long as a register is locked. While a register is locked, writes to this register
are ignored.
Each of the registers in the KAPWR region have a key that can be in one of two states: open
or locked. At power-on reset the following keys are locked by default: RTC, RTSEC,
RTCAL, and RTCSC. All other registers are unlocked. Each key has an address associated
with it in the internal map.
A write of 0x55CCAA33 to the associated key register changes the key to the open state.
A write of any other data to this location changes the key to the locked state. The key
registers are write-only. A read of the key register has undefined side effects and may be
interpreted as a write that locks the associated register.
Table 8-8 lists the registers powered by KAPWR and the associated key registers.
Table 8-8. KAPWR Registers and Key Registers
KAPWR Register
Address or
SPR Number
0x2F C200 Time Base Status and Control (TBSCR)
See Table 6-18 for bit descriptions.
0x2F C204 Time Base Reference 0 (TBREF0)
See Section 6.2.2.4.3, "Time Base
Reference Registers (TBREF0 and
TBREF1)" for bit descriptions.
0x2F C208 Time Base Reference 1 (TBREF1)
See Section 6.2.2.4.3, "Time Base
Reference Registers (TBREF0 and
TBREF1) for bit descriptions.
0x2F C220 Real Time Clock Status and Control
(RTCSC)
See Table 6-19 for bit descriptions. This
register is locked after RESET by default.
0x2F C224 Real Time Clock (RTC)
See Section 6.2.2.4.6, "Real-Time Clock
Register (RTC)" for bit descriptions. This
register is locked after RESET by default.
0x2F C228 Real Time Alarm Seconds (RTSEC)
Reserved. This register is locked after
RESET by default.
0x2F C22C Real Time Alarm (RTCAL)
See Section 6.2.2.4.7, "Real-Time Clock
Alarm Register (RTCAL)" for bit
descriptions. This register is locked after
RESET by default.
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Register
Chapter 8. Clocks and Power Control
Associated Key Register
Address
0x2F C300 Time Base Status and Control Key
(TBSCRK)
0x2F C304 Time Base Reference 0 Key (TBREF0K)
0x2F C308 Time Base Reference 1 Key (TBREF1K)
0x2F C320 Real Time Clock Status and Control Key
(RTCSCK)
0x2F C324 Real Time Clock Key (RTCK)
0x2F C328 Real Time Alarm Seconds Key (RTSECK)
0x2F C32C Real Time Alarm Key (RTCALK)
Basic Power Structure
Register
8-25