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to SCSI, 4 bytes (on long word) of data is loaded from memory
at a time.
It is then divided up byte by byte and written to
CXD1180.
When data is transferred from SCSI to memory, the
data read from the 1180 is packed into one long word and
written to memory.
A built-in address conversion table is
used when memory is accessed.
This allows even data scattered
at nonconsecutive memory areas to be accessed as if it were
all in one contiguous area.
Using the table, it is possible
to transfer a maximum of 516K bytes of data at one time.
MEMC
performs memory usage arbitration.
Flowcharts for data transfers from memory to SCSI and from
SCSI to memory are given below.
a) Memory to SCSI transfer
<Memory>
<Peripheral>
<MEMC>
< DMAC >
<
1180
>
[
OREO output
DMBR2 output
--
J
Memory arbitration
•
DMBG2 output
Address selector
•
Memory address
set to OMA
output
ROW address
--
--
input
-
_i
,
DMAS output
•
RASO output
•
ROW address
--
latched
-
'
Address selector
--
set to CLO
,
CAS output
CAS decoder
. .
,
output
COL address
latched
•
1
DMDSACK output
Data output
-"
.....
•
NWS-1510/1530/1580
3-33
I
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