Memory Banks & Programming Rs-485; Using Memory Bank - Sony 486DX User Manual

9. MEMORY BANKS & PROGRAMMING RS-485

9.1 USING MEMORY BANK

This section provides the information about how to access the memory on the AR-B1474 without using the AR-
B1474 SSD BIOS. The AR-B1474 hardware divides every 8K bytes of memory into a memory bank. To access the
data in the memory, you have to assign the chip number and the bank number. On every chip, the memory bank
number starts from zero. The last memory bank number depends on the size of the memory chip used on the AR-
B1474. For example, if you use the 256K bytes memory chip, the bank number on every chip would be in the
range of 0 to 31. The chip numbers and the bank numbers are determined by the bank select register on the AR-
B1474.
The I/O addresses of these registers are determined by SW1-1and SW1-2. The memory address of the memory
bank is located on the range selected by SW1-3 and SW1-4.
The I/O port address of the bank select register is base port+0. The following is the format of the bank select
register and bank enable register.
Where:
CS1-CS0 : Chip select
For different types of memory, K0 to K5 have different explanations. These bits are used to select the bank number
of specific memory located in CS0 and CS1.
NOTE: BS0 to BS5 are the memory bank select bits. For example, 128KB memory has sixteen 8K-byte banks, so
4 bits (BS0 to BS3) are needed, and 512KB memory needs 6 bits (BS0 to BS5), etc.
BASE+0
D7 D6 D5
CS1 CS0 K5
CS1
0
0
1
1
Memory
64KB EPROM (FLASH)
128KB EPROM (FLASH)
256KB EPROM (FLASH)
512KB EPROM (FLASH)
128KB SRAM
512KB SRAM
D4 D3 D2
K4 K3 K2
CS0
0
1
0
1
K5 K4 K3 K2
0 1 0 BS2
0 1 BS3 BS2
BS4 1 BS3 BS2
BS4 BS5 BS3 BS2
1 0 BS3 BS2
BS5 BS4 BS3 BS2
AR-B1474 User¡ ¦ s Guide
D1 D0
K1 K0
Socket
Disable
MEM1
MEM2
MEM3
K1 K0
BS1 BS0
BS1 BS0
BS1 BS0
BS1 BS0
BS1 BS0
BS1 BS0
9-1