DS3134 datasheet(117/203 Pages) DALLAS

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DS3134

117 of 203

RECEIVE DMA CONFIGURATION RAM Figure 8.1.5A

- FOR DMA USAGE ONLY / HOST CAN ONLY READ THIS FIELD -

dword 0; Bits 0 to 31 / Current Data Buffer Address. The current 32-bit address of the data buffer that

is being used. This address is used by the DMA to keep track of where data should be written to as it

comes in from the Receive FIFO.

- FOR DMA USAGE ONLY / HOST CAN ONLY READ THIS FIELD -

dword 1; Bits 0 to 15 / Current Descriptor Pointer. This 16-bit value is the offset from the Receive

Descriptor Base Address of the current Receive Descriptor being used by the DMA to describe the

specifics of the data being stored in the associated data buffer.

- FOR DMA USAGE ONLY / HOST CAN ONLY READ THIS FIELD -

dword 1; Bits 16 to 31 / Starting Descriptor Pointer. This 16-bit value is the offset from the Receive

Descriptor Base Address of the first Receive Descriptor in a link-list chain of descriptors. This pointer

will be written into the Done Queue by the DMA after a specified number of data buffers (see the

Threshold value below) have been filled.

- HOST MUST CONFIGURE -

dword 2; Bit 0 / Channel Enable (CHEN).

This bit is controlled by the host to enable and disable a

HDLC channel.

0 = HDLC Channel Disabled

1 = HDLC Channel Enabled

dmarcram

msb

lsb

Receive DMA Configuration RAM

000h

004h

008h

HDLC

Channel

00Ch

010h

014h

HDLC

Channel

BF4h

BF8h

BFCh

HDLC

Channel

256

Fields shown within the thick box

are written by the Host; all other

fields are for usage by the DMA and

can only be read by the Host

Current Descriptor Pointer (16)

Start Descriptor Pointer (16)

Byte Count (13)

Threshold

Count (3)

Threshold(3) Offset (4)

Size

(2)

Current Descriptor Pointer (16)

Current Packet Data Buffer Address (32)

Start Descriptor Pointer (16)

Byte Count (13)

Threshold

Count (3)

Threshold(3) Offset (4)

Size

(2)

Current Descriptor Pointer (16)

Start Descriptor Pointer (16)

Byte Count (13)

Threshold

Count (3)

Threshold(3) Offset (4)

Size

(2)

Current Packet Data Buffer Address (32)

unused (5)

FBF

unused (5)

FBF

unused (5)

FBF

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