Configuring Dma And Interrupt Settings - Creative SB0350 Programming Manual

2-6 Introduction to DSP Programming
The following assembly code fragment illustrates the interrupt handling portion
within a 16-bit DMA mode digitized sound I/O ISR:
interrupt?
instructions
ChainPreviousISR:
ExitISR:

Configuring DMA and Interrupt Settings

With the DSP version 4.xx, the DMA channels Interrupt Request (IRQ) line are
software configurable. The Interrupt Setup register, addressed as register 80h on
the Mixer register map, is used to configure or determine the Interrupt Request line.
The DMA Setup register, addressed as register 81h on the Mixer register map, is
used to configure or determine the DMA channels.
Reading and writing the register 80h and 81h are accomplished in the same manner
as reading and writing any of the other mixer registers (see the chapter "Mixer Chip
Programming").
The byte from register 80h is interpreted as follows:
dx,wSB16BaseAddx ; SB16 base I/O address 2 x 0h
mov
add dl,4
mov al,82h
out dx,al
inc dx
in al,dx
test al,02h
jz ChainPreviousISR ; No, chain to previous ISR
;***
;*** 1). Perform your 16-bit DMA digitized sound I/O
;*** 2). Acknowledge the DSP interrupt; in
;*** 3). Send EOI to the Programmable Interrupt Controller
;***
jmp ExitISR
;***
;*** Chain to previous ISR
D7 D6 D5 D4
; Mixer register address port 2 x 4h
; Index for Interrupt Status register
; Mixer data port
; Get interrupt status
; 16-bit DMA-mode digitized sound I/O
D3 D2 D1
IRQ10 IRQ7 IRQ5
al,2 x Fh
D0
IRQ2