Jameco Electronics Rabbit 3000 User Manual
Page 307
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