PCM-C418/Configuration
v1.0
www.winsystems.com
Page 32
For example, the DOS driver
USSD.SYS
can be used to make the SRAM appear as a
drive in the system by adding the following to
config.sys
.
Device = c:\ussd.sys /mod:u /pad:220 /dsz:1024
The base address for the SRAM is located at
0220h
.
There are four I/O registers used for accessing the memory array. The register definition
and usage is defined below.
This register is write-only and holds the upper 8 bits of the 24-bit address used to
access the 1 MB SRAM.
This register is write-only and holds the middle 8 bits of address used to access the
1 MB memory array. Writing this register also clears the LSB address counter to 0.
Table 19:
Offset 0
OFFSET 0 - MSB Address Register
D7 - A23 of access address
D6 - A22 of access address
D5 - A21 of access address
D4 - A20 of access address
D3 - A19 of access address
D2 - A18 of access address
D1 - A17 of access address
D0 - A16 of access address
Table 20:
Offset 1
OFFSET 1 - NSB Address Register
D7 - A15 of access address
D6 - A14 of access address
D5 - A13 of access address
D4 - A12 of access address
D3 - A11 of access address
D2 - A10 of access address
D1 - A9 of access address
D0 - A8 of access address
