Motorola MVME172 - Manual (Page 317)

Programming Model
http://www.mcg.mot.com/literature 5-27
5
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.
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