HP XA Function, Function, DMA controller, I/O Address Ports, DMA Channel Controllers

4 HP BIOS

BIOS Addresses

I/O Address Ports	Function
0378 - 037A	LPT1
0388 - 038B	AD1816 Ad-lib (FM)
03B0 - 03DF	VGA
03E8 - 03EF	COM3
03F0h- 03F5	Flexible disk drive controller
03F6	IDE primary channel
03F7	Flexible disk drive controller
03F8 - 03FF	COM1
04D0 - 04D1	Interrupt edge/level control
0678 - 067B	LPT2 ECP
0778 - 077B	LPT1 ECP
0CF8 - 0CFF	PCI configuration space

DMA Channel Controllers

Only “I/O-to-memory” and “memory-to-I/O” transfers are allowed. “I/O-to-I/O” and “memory-to-memory” transfers are disallowed by the hardware configuration.

The system controller supports seven DMA channels, each with a page register used to extend the addressing range of the channel to 16 MB. The following table summarizes how the DMA channels are allocated.

	DMA controller
Channel		Function
0		AD1816 Capture
1		AD1816 Playback
2		NS317 Flexible disk controller
3		NS317 LPT ECP
4		Used to cascade DMA channels 0-3
5		Free
6		Free
7		Free

82