Motorola MVME172 manual Programmable Clock General Control Register, PS2-0, Clr

Models: MVME172

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4

IP2 Chip

Programmable Clock General Control Register

ADR/SIZ

 

 

 

 

 

$FFFBC081 (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

7

6

 

 

5

 

4

 

3

 

2

 

 

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NAME

PLTY

PLS

 

 

0

 

 

EN

 

CLR

 

PS2

 

PS1

 

PS0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OPER

R/W

R/W

 

 

R

 

 

R/W

 

R/W

 

R/W

 

R/W

 

R/W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

0 R

0 R

 

 

0 R

 

 

0 R

 

0 R

 

0 R

 

0 R

 

0 R

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PS2-0

 

These three bits select the frequency of the pre-scale logic

 

 

 

output The MC68060 bus clock (BCK) is used as the input

 

 

 

to the pre-scale logic. BCK is ether 25 MHz or 32 MHz.

 

 

 

BCK frequency can be determined by examining the

 

 

 

Version Register in the MC2 chip ASIC.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PS2-PS0

 

 

Pre-scaler Output Frequency

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PLS = 0

 

 

 

PLS = 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

BCK/2

 

 

 

No Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

BCK/4

 

 

 

BCK/2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

BCK/8

 

 

 

BCK/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

BCK/16

 

 

 

BCK/8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

BCK/32

 

 

 

BCK/16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

BCK/64

 

 

 

BCK/32

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

 

 

BCK/128

 

 

 

BCK/64

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

 

 

 

BCK/256

 

 

 

BCK/128

 

CLR

 

 

 

 

 

 

 

Setting this bit forces the programmable clock’s internal

 

 

 

registers (except for the interrupt and general control

 

 

 

registers) to zero. These registers include the pre-scaler

 

 

 

and timer counters. Note that these registers will remain

 

 

 

cleared until the CLR bit is set to a zero.

 

 

 

 

EN

 

When the EN bit is set, the programmable clock is

 

 

 

 

enabled. When it is cleared, the programmable clock is

 

 

 

suspended. EN performs its function by

 

 

 

4-44

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Motorola MVME172 manual Programmable Clock General Control Register, PS2-0, Clr