DS3134 datasheet(142/203 Pages) DALLAS

142 / 203 page

DS3134

142 of 203

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

dword 1; Bits 18 to 19 / Pending State (PENDST). This field is used by the transmit DMA to keep

track of queued descriptors as they arrive from the Pending Queue and for the DMA to know when it

should create a horizontal linked list of transmit descriptors and where it can find the next valid

descriptor. This field handles standard packets and the PRIST field handles priority packets.

State

Next Descriptor

Next Pending Descriptor

Pointer field

not valid

valid

not valid

valid

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

dword 1; Bits 20 to 21 / Priority State (PRIST). This field is used by the transmit DMA to keep track

of queued priority descriptors as they arrive from the Pending Queue and for the DMA to know when it

should create a horizontal linked list of transmit priority descriptors and where it can find the next valid

priority descriptor. This field handles priority packets and the PENDST field handles standard packets.

State

Next Priority Descriptor

Next Priority Pending

Pointer field

Descriptor Pointer field

not valid

valid

not valid

valid

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

dword 1; Bit 22/ Processing Priority Packet (PPP). This bit will be set to a one when the DMA is

currently processing a priority packet.

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

dword 1; Bits 23 to 31/ Unused. This field is not used by the DMA and could be any value when read

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

dword 2; Bits 0 to 15 / Next Descriptor Pointer. This 16-bit value is the offset from the Transmit

Descriptor Base Address of the next Transmit Packet Descriptor for the packet that is currently being

transmitted. Only valid if EOF = 0 or if EOF = 1 and CV = 1.

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

dword 2; Bits 16 to 31 / Start Descriptor Pointer. This 16-bit value is the offset from the Transmit

Descriptor Base Address of the first Transmit Packet Descriptor for the packet that is currently being

transmitted. If DQS = 0, then this pointer is written back to the Done Queue when the packet has

completed transmission. This field is used by the DMA for processing standard as well as priority

packets.

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

dword 3; Bits 0 to 15 / Next Pending Descriptor Pointer. This 16-bit value is the offset from the

Transmit Descriptor Base Address of the first Transmit Packet Descriptor for the packet that is queued up

next for transmission.

DS3134 Datasheet(PDF) 142 Page - Dallas Semiconductor

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