Motorola MPC823e - Decrementer Register

System Interface Unit
MOTOROLA MPC823e REFERENCE MANUAL 12-13
SYSTEM INTERFACE UNIT
12
12.5.1 Decrementer Register
The 32-bit decrementer (DEC) register is a special-purpose register defined by PowerPC
architecture. The decrementer causes an interrupt whenever Bit 0 changes from a logic 0 to
a logic 1. The contents of this register can be read or written to by the mfspr or mtspr
instruction. This register is undefined at reset. The decrementer is powered by standby
power and continues counting when standby power is applied. To enable the decrementer
control bits, use the timebase control and status register. The decrementer and timebase
share the same TMBCLK.
DEC—Decrementer
This field is used by a down counter to cause decrementer interrupts. A read of this register
always returns the current count value from the down counter.
DEC
BIT
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
FIELD DEC
RESET —
R/W R/W
SPR 22
BIT
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
FIELD DEC
RESET —
R/W R/W
SPR 22
NOTE: — = Undefined.