PD6710 Datasheet, PDF (37/138 Pages) Intel Corporation – ISA-to-PC-Card (PCMCIA) Controllers

ISA-to-PC-Card (PCMCIA) Controllers — PD6710/’22
The Index register (see “Operation Registers” on page 41) is used to specify which of the internal
registers the CPU will access next. The value in the Index register is called the Register Index.
This number specifies a unique internal register. The Data register is used by the CPU to read and
write the internal register specified by the Index register.
Figure 8. Indexed 8-Bit Register Structure
Internal Registers
FFh
FEh Register
• Indexes
•
•
02h
01h
00h
High Byte
Low Byte
Data
Index
3E1h
3E0h
I/O Addresses
Figure 9. Indexed 8-Bit Register Example
The following code segment demonstrates use
of an indexed 8-bit register:
mov dx, 3E0h
mov al, 02h
mov ah, 3Ch
out dx, ax
Internal Registers
Register
Indexes
3Ch
02h
AH
AL
3Ch
02h
3E1h
3E0h
I/O Addresses
Double-Indexed Registers
The PD67XX has Extension registers that add to the functionality of the 82365SL-compatible
register set. Within the Extension registers is an Extended Index register and Extended Data
register that provide access to more registers. The registers accessed through Extended Index and
Extended Data are thus double indexed. The example below shows how to access the Extension
Control 1 register, one of the double-indexed registers.
;Write to Extension Control 1 register example
;Constants section
Extended_Index
EQU 2Eh
Index_Reg
EQU 2Fh
Ext_Cntrl_1
EQU 03h
PD67XX_Index
EQU 3E0h
;Code section
mov
dx, PD67XX_Index
mov
al, Extended_Index
mov
ah, Ext_Cntrl_1
Datasheet
37