Programming Model

Note that if STON2-0 is zero, the scrubber always releases the DRAM after one memory cycle, even if neither the local bus nor refresher need it.

SRDIS SRDIS disables the scrubber from performing reads during scrub cycles. This mode should only be used when using the scrub function to perform zero fill of the DRAM. Setting this bit causes the zero fill to happen faster. This bit should not be changed while scrubbing is in process.

5

Scrub Prescaler Counter (Bits 21-16)

The Scrub Prescaler Counter uses the 1MHz clock as an input to create the

.5 Hz clock that is used for the scrub period. Writes to this address update the scrub prescaler. Reads to this address yield the value in the scrub prescaler. The ability to read and write to the scrub prescaler is provided for test purposes. Programming this counter is not recommended. This register reflects the current value in the scrub prescaler bits 21-16.

ADR/SIZ

 

 

1st $FFF43038/2nd $FFF43138 (8-bits)

 

 

 

 

 

 

 

 

 

 

 

BIT

31

30

 

29

28

27

26

25

24

 

 

 

 

 

 

 

 

 

 

NAME

0

0

 

SPS21

SPS20

SPS19

SPS18

SPS17

SPS16

 

 

 

 

 

 

 

 

 

 

OPER

R/W

R/W

 

R/W

R/W

R/W

R/W

R/W

R/W

 

 

 

 

 

 

 

 

 

 

RESET

0 PLS

0 PLS

 

0 PLS

0 PLS

0 PLS

0 PLS

0 PLS

0 PLS

 

 

 

 

 

 

 

 

 

 

http://www.mcg.mot.com/literature

5-27

Page 317
Image 317
Motorola MVME172 manual Scrub Prescaler Counter Bits