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298 Rabbit 3000 Microprocessor
B.1.12.1 Clock Select and Power Save Modes
Table B-24 outlines the power save modes available in the Rabbit 3000A. The GCSR is
shown in Table B-23 for reference.
Table B-23. Global Control/Status Register
Global Control/Status Register (GCSR) (Address = 0x00)
Bit(s) Value Description
7:6
(rd-only)
00 No reset or watchdog timer time-out since the last read.
01
The watchdog timer timed out. These bits are cleared by a read of this
register.
10 This bit combination is not possible.
11 Reset occurred. These bits are cleared by a read of this register.
5
0 No effect on the periodic interrupt. This bit will always be read as zero.
1 Force a periodic interrupt to be pending.
4:2 xxx See table below for decode of this field.
1:0
00 Periodic interrupts are disabled.
01 Periodic interrupts use Interrupt Priority 1.
10 Periodic interrupts use Interrupt Priority 2.
11 Periodic interrupts use Interrupt Priority 3.
Table B-24. Clock Select Field of GCSR
Clock Select
Bits 4:2 GCSR
CPU Clock
Peripheral
Clock
Main
Oscillator
Power-Save CS
if Enabled by
GPSCR
000 osc/8 osc/8 on short CS option
001 osc/8 osc on short CS option
010 osc osc on none
011 osc/2 osc/2 on short CS option
100 32 kHz or fraction 32 kHz or fraction on
self-timed option
short CS option
101 32 kHz or fraction 32KHz or fraction off
self-timed option
short CS option
110 osc/4 osc/4 on short CS option
111 osc/6 osc/6 on short CS option