Sundance-spas ST201 Bedienungsanleitung PDF herunterladen (Seite 81)

Sundance Technology ST201 PRELIMINARY draft 2

TXDMAURGENTTHRESH

Class....................I/O Registers, DMA

Base Address ......IoBaseAddress register value

Address Offset.....0x09

Access Mode.......Read/Write

Width ...................8 bits

When the number of used bytes in the TxFIFO falls below the value in the TxDMAUrgentThresh, the

TxDMA Logic will make an urgent bus master request. An urgent TxDMA request will have priority over the

RxDMA, unless it is also making an urgent request. A TxDMA urgent request is not subject to the

TxDMABurstThresh constraint. The relaxation of the TxDMABurstThresh constraint for this condition is

because the TxFIFO is close to under run, and burst efficiency is sacrificed to avoid FIFO under run. The

value in TxDMAUrgentThresh represents data in the TxFIFO in multiples of 32 bytes. TxDMAUrgent-

Thresh resets to 4, or a threshold of 128 bytes.

BIT BIT NAME BIT DESCRIPTION

5..0 TxDMAUrgent-

Thresh

The minimum number of 32-byte words which must be occupied in the

TxFIFO to avoid assertion of a TxDMA Urgent Request.

7..6 Unused These bits are ignored.

1 2 ... 76 77 78 79 80 81 82 83 84 85 86 ... 144 145

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Sundance-spas ST201 Bedienungsanleitung Seite 81