AMD SC1201, SC1200 manual Audio Bus Master 4 Command Register R/W Reset Value 00h, Offset 42h-43h

Core Logic Module - Audio Registers - Function 3 32579B

Table 6-38. F3BAR0+Memory Offset: Audio Configuration Registers (Continued)

Bit	Description
Offset 40h	Audio Bus Master 4 Command Register (R/W)	Reset Value: 00h

Audio Bus Master 4: Output to codec; 16-Bit; Slot 6 or 11 (F3BAR0+Memory Offset 08h[19] selects slot).

7:4 Reserved. Must be set to 0. Must return 0 on reads.

3Read or Write Control. Set the transfer direction of Audio Bus Master 4.

0:PCI reads are performed.

1:PCI writes are performed.

	This bit must be set to 0 (read) and should not be changed when the bus master is active.
2:1	Reserved. Must be set to 0. Must return 0 on reads.

0Bus Master Control. Controls the state of the Audio Bus Master 4.

0:Disable.

1:Enable.

Setting this bit to 1 enables the bus master to begin data transfers. When writing 0 to this bit, the bus master must be either paused or have reached EOT. Writing 0 to this bit while the bus master is operating, results in unpredictable behavior (and may crash the bus master state machine). The only recovery from this condition is a PCI reset.

Offset 41h Audio Bus Master 4 SMI Status Register (RC) Reset Value: 00h

Audio Bus Master 4: Output to codec; 16-Bit; Slot 6 or 11 (F3BAR0+Memory Offset 08h[19] selects slot).

7:2 Reserved.

1Bus Master Error. Indicates if hardware encountered a second EOP before software cleared the first.

0:No.

1:Yes.

If hardware encounters a second EOP (end of page) before software cleared the first, it causes the bus master to pause until this register is read to clear the error.

0End of Page. Bus master transferred data which is marked by the EOP bit in the PRD table (bit 30).

0:No.

1:Yes.

Offset 42h-43h	Not Used
Offset 44h-47h	Audio Bus Master 4 PRD Table Address (R/W)	Reset Value: 00000000h

Audio Bus Master 4: Output to codec; 16-Bit; Slot 6 or 11 (F3BAR0+Memory Offset 08h[19] selects slot).

31:2	Pointer to the Physical Region Descriptor Table. This register is a PRD table pointer for Audio Bus Master 4.
	When written, this register points to the first entry in a PRD table. Once Audio Bus Master 4 is enabled (Command Register
	bit 0 = 1), it loads the pointer and updates this register (by adding 08h) so that it points to the next PRD.
	When read, this register points to the next PRD.
1:0	Reserved. Must be set to 0.

Note: The Physical Region Descriptor (PRD) table consists of one or more entries - each describing a memory region to or from which data is to be transferred. Each entry consists of two DWORDs.

DWORD 0:	[31:0]	= Memory Region Physical Base Address
DWORD 1:	31	= End of Table Flag
	30	= End of Page Flag
	29	= Loop Flag (JMP)
	[28:16]	= Reserved (0)
	[15:0]	= Byte Count of the Region (Size)

AMD Geode™ SC1200/SC1201 Processor Data Book 275