PCM-C418/Configuration
v1.0
www.winsystems.com
Page 33
This read/write register is the primary window to the memory array. A value written to
this port is written to the address in the memory array specified by the MSB register, the
NSB register, and the current LSB counter address. In like fashion, a read from this I/O
address results in the current memory array data at the address specified by the MSB
register, the NSB register, and the LSB address counter.
In either case, read or write, an access to this register results in the LSB address
counter being incremented immediately following the access so that the next access is
at the next sequential address in the array. This incrementing process does
not
carry
into the NSB or MSB register which must be rewritten every 256 bytes.
This read/write register is used to access the memory array when post incrementing of
the LSB counter is not desired. The byte written or read is still specified by the 24-bit
combination of the MSB register, the NSB register, and the LSB counter. However, the
LSB counter is
not
altered following the access. It is then necessary to do one more
read from Data Access Register A to bump the address to the next byte.
Table 21:
Offset 2
OFFSET 2 - Data Access Register A
D7 - D7 of memory data
D6 - D6 of memory data
D5 - D5 of memory data
D4 - D4 of memory data
D3 - D3 of memory data
D2 - D2 of memory data
D1 - D1 of memory data
D0 - D0 of memory data
Table 22:
Offset 3
OFFSET 3 - Data Access Register B
D7 - D7 of memory data
D6 - D6 of memory data
D5 - D5 of memory data
D4 - D4 of memory data
D3 - D3 of memory data
D2 - D2 of memory data
D1 - D1 of memory data
D0 - D0 of memory data
