Creative SB0350 Hardware Programming Guide - Page 60

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4-2 Mixer Chip Programming Programming Sequence Each mixer chip uses two consecutive I/O ports: 2x4h and 2x5h where x depends on the jumper selectable setting of the base I/O address. Port 2x4h is the write-only Address Port. Port 2x5h is the Data Port which can be read or written. The sequence for programming a mixer chip is as follows: 1. 2. write the index of the mixer register to the Address Port. write/read the mixer register value to/from the Data Port. The following assembly code fragment shows the process of accessing a mixer register: ; Common setup code ; Specify which register to access ; mov dx,wSBCBaseAddx ; Base I/O address add dx,4 ; Mixer address port mov al,bMixerRegIndex ; Index of mixer's register out dx,al ; Select the register inc dx ; Mixer data port ; Write to the mixer register ; mov al,bMixerRegSetting ; Set the register setting out dx,al ; Read from the mixer register ; mov al,bMixerRegSetting ; Retrieve the register setting in al,dx

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4-2
Mixer Chip Programming
Programming Sequence
Each mixer chip uses two consecutive I/O ports:
2
x
4h
and
2
x
5h
where
x
depends on
the jumper selectable setting of the base I/O address.
Port 2
x
4h is the write-only
Address Port. Port 2
x
5h is the Data Port which can be read or written.
The sequence for programming a mixer chip is as follows:
1.
write the index of the mixer register to the Address Port.
2.
write/read the mixer register value to/from the Data Port.
The following assembly code fragment shows the process of accessing a mixer
register:
; Common setup code
; Specify which register to access
;
mov
dx,wSBCBaseAddx
; Base I/O address
add
dx,4
; Mixer address port
mov
al,bMixerRegIndex
; Index of mixer's register
out
dx,al
; Select the register
inc
dx
; Mixer data port
; Write to the mixer register
;
mov
al,bMixerRegSetting
; Set the register setting
out
dx,al
; Read from the mixer register
;
mov
al,bMixerRegSetting
; Retrieve the register setting
in
al,dx