dmaen.asm

;Code from PC XT Turbobios (phatcode)
	
	.8086
	org	100h

	mov	al, 01010100b			; IC 8253 inits memory refresh
	out	43h, al 			;   chan 1 pulses IC 8237 to
	mov	al, 12h 			;   DMA every 12h clock ticks
	out	41h, al 			;   64K done in 1 millisecond
	mov	al, 01000000b			; Latch value 12h in 8253 clock
	out	43h, al 			;   chip channel 1 counter

	mov	al, 0				; Do some initialization
	out	81h, al 			;   DMA page reg, chan 2
	out	82h, al 			;   DMA page reg, chan 3
	out	83h, al 			;   DMA page reg, chan 0,1
	out	0Dh, al 			; Stop DMA on 8237 chip
	mov	al, 01011000b			; Refresh auto-init dummy read
	out	0Bh, al 			;   on channel 0 of DMA chip
	mov	al, 01000001b			; Block verify
	out	0Bh, al 			;   on channel 1 of DMA chip
	mov	al, 01000010b			; Block verify
	out	0Bh, al 			;   on channel 2 of DMA chip
	mov	al, 01000011b			; Block verify
	out	0Bh, al 			;   on channel 3 of DMA chip
	mov	al, 0FFh			; Refresh byte count
	out	1, al				;   send lo order
	out	1, al				;   send hi order
	inc	ax				; Initialize 8237 command reg
	out	8, al				;   with zero
	out	0Ah, al 			; Enable DMA on all channels
	
	ret