B.1.12.1 Clock Select and Power Save Modes

Table B-24outlines the power save modes available in the Rabbit 3000A. The GCSR is shown in Table B-23for reference.

Table B-23. Global Control/Status Register

Global Control/Status Register

(GCSR)

(Address = 0x00)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

 

00

No reset or watchdog timer time-out since the last read.

 

 

 

7:6

01

The watchdog timer timed out. These bits are cleared by a read of this

register.

 

 

 

 

 

(rd-only)

 

 

 

 

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.

 

 

 

 

 

 

00

Periodic interrupts are disabled.

 

 

 

 

 

1:0

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

 

Peripheral

Main

Power-Save CS

CPU Clock

if Enabled by

Bits 4:2 GCSR

Clock

Oscillator

 

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

 

 

 

 

 

298

Rabbit 3000 Microprocessor

Page 307
Image 307
Jameco Electronics 2000, 3000 manual Table B-23. Global Control/Status Register, Table B-24. Clock Select Field of Gcsr