Specifications

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:
mov dx,wSB16BaseAddx ; SB16 base I/O address 2 x 0h
add dl,4 ; Mixer register address port 2 x 4h
mov al,82h ; Index for Interrupt Status register
out dx,al
inc dx ; Mixer data port
in al,dx ; Get interrupt status
test al,02h ; 16-bit DMA-mode digitized sound I/O
interrupt?
jz ChainPreviousISR ; No, chain to previous ISR
;***
;*** 1). Perform your 16-bit DMA digitized sound I/O
instructions
;*** 2). Acknowledge the DSP interrupt; in al,2 x Fh
;*** 3). Send EOI to the Programmable Interrupt Controller
;***
jmp ExitISR
ChainPreviousISR:
;***
;*** Chain to previous ISR
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:
D7 D6 D5 D4 D3 D2 D1 D0
IRQ10 IRQ7 IRQ5 IRQ2
where the grayed areas denote reserved bits.
To configure the IRQ setting, set the corresponding interrupt bit to '1' to select the
IRQ. Note that only a bit can be set on at any one time.