VT8235 datasheet(121/145 Pages) VIA

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VT8235 V-Link South Bridge

Revision 1.22 October 24, 2002

-115-

Device 17 Function 6 Modem Controller Registers

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I/O Base 0 Regs – Modem Scatter / Gather DMA

Modem SGD Read Channel Registers

I/O Offset 40 – Modem SGD Read Channel Status.....RWC

SGD Active ......................................................... RO

SGD has completed or been terminated default

SGD Active

SGD Paused ......................................................... RO

SGD not paused..................................... default

SGD Paused

5-4

Reserved

........................................ always reads 0

SGD Trigger Queued .......................................... RO

This bit reports whether the trigger used to restart the

SGD operation is queued (I/O Offset 41[1] = 1 while

the SGD engine is running).

SGD trigger not queued......................... default

SGD trigger queued (when SGD reaches EOL,

it will restart).

SGD Stop Interrupt Status..............................RWC

SGD finished the index equal to the stop index

set in 4B-48[31-24].

SGD EOL (End Of Link).................................RWC

Block is the last of the link. May be used by

software as a signal to generate an interrupt

request if I/O Offset 41[1] = 1.

SGD Flag

......................................................RWC

Block complete. May be used by software as a

signal to generate an interrupt request if I/O

Offset 41[0] = 1.

I/O Offset 41 – Modem SGD Read Channel Control .....RW

SGD Start

............................ WO (always reads 0)

No effect

Start SGD read channel operation

SGD Terminate ...................... WO (always reads 0)

No effect

Terminate SGD read channel operation

5-4

Test (Do Not Program)

.......................always write 0

SGD Pause .........................................................RW

Release SGD read channel pause and resume

the transfer from the paused line

Pause SGD read channel operation (SGD read

channel pointer stays at the current address)

2-0

Reserved

........................................ always reads 0

I/O Offset 42 – Modem SGD Read Channel Type ......... RW

Auto-Start SGD at EOL

Stop at EOL ........................................... default

Auto restart at EOL

6-4

Reserved

........................................always reads 0

3-2

Interrupt Select

This bit determines the timing of interrupt generation

when bit-1 or bit-0 of this register are equal to 1.

00 Interrupt at PCI Read of Last Line......... default

01 Interrupt at Last Sample Sent

10 Interrupt at Less Than One Line to Send

11 -reserved-

Interrupt on EOL @ End of Block

Disable ................................................... default

Enable

Interrupt on FLAG @ End-of-Blk

Disable ................................................... default

Enable

I/O Offset 47-44 – Modem SGD R Ch Table Ptr Base... RW

31-0 SGD Table Pointer Base Address (even addr) .... W

Current Pointer Address ....................................... R

I/O Offset 4F-4C – Modem SGD R Ch Current Count .. RO

31-24 Current Modem SGD Read Channel Index

This field reports the index the SGD engine is

currently processing.

23-0 Current Modem SGD Read Channel Count

This field reports the count remaining in the current

entry being processed. For example, if 10 bytes of a

30-byte count have been transferred, this field would

read 20 to indicate 20 bytes remaining.

Modem SGD Table Format

60-56

55-32

31-0

EOL FLAG STOP

-reserved-

Base

Count

Address

[23:0]

[31:0]

VT8235 Datasheet(PDF) 121 Page - VIA Technologies, Inc.

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