3

MC2 Chip

Tick Timer 3 and 4 Control Registers

Tick Timer 4 Control Register

ADR/SIZ

 

 

 

$FFF4201C (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

15

14

13

 

12

11

 

10

9

8

 

 

 

 

 

 

 

 

 

 

 

NAME

OVF3

OVF2

OVF1

 

OVF0

 

 

COVF

COC

CEN

 

 

 

 

 

 

 

 

 

 

 

OPER

R

R

R

 

R

R

 

C

R/W

R/W

 

 

 

 

 

 

 

 

 

 

 

RESET

0 PL

0 PL

0 PL

 

0 PL

0

 

0 PL

0 PL

0 PL

 

 

 

 

 

 

 

 

 

 

 

Tick Timer 3 Control Register

 

 

 

 

 

 

 

 

 

 

 

 

 

ADR/SIZ

 

 

 

$FFF4201C (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

7

6

5

 

4

3

 

2

1

0

 

 

 

 

 

 

 

 

 

 

 

NAME

OVF3

OVF2

OVF1

 

OVF0

 

 

COVF

COC

CEN

 

 

 

 

 

 

 

 

 

 

 

OPER

R

R

R

 

R

R

 

C

R/W

R/W

 

 

 

 

 

 

 

 

 

 

 

RESET

0 PL

0 PL

0 PL

 

0 PL

0

 

0 PL

0 PL

0 PL

 

 

 

 

 

 

 

 

 

 

 

CEN When this bit is high, the counter increments. When this bit is low, the counter does not increment.

COC When this bit is high, the counter is reset to zero when it compares with the compare register. When this bit is low, the counter is not reset.

COVF The overflow counter is cleared when a one is written to this bit.

OVF3-OVF0

These bits are the output of the overflow counter. The overflow counter is incremented each time the tick timer sends an interrupt to the local bus interrupter. The overflow counter can be cleared by writing a one to COVF.

3-24

Computer Group Literature Center Web Site

Page 212
Image 212
Motorola MVME172 manual Tick Timer 3 and 4 Control Registers, Tick Timer 4 Control Register, Tick Timer 3 Control Register