Sundance Spas ST201 manual Rxdmaurgentthresh

Sundance Technology

ST201

PRELIMINARY draft 2

RXDMAURGENTTHRESH

Class	I/O Registers, DMA
Base Address	IoBaseAddress register value
Address Offset	0x15
Access Mode	Read/Write
Width	8 bits

The value in RxDMAUrgentThresh sets a threshold at which the RxDMA engine will make a urgent bus master request. A urgent RxDMA request will have priority over all other requests on the ST201. The urgent bus request is made when the free space in the RxFIFO falls below the value in RxDMAUrgent- Thresh. A RxDMA urgent request is not subject to the RxDMABurstThresh constraint. When the RxFIFO is close to overrun, burst efficiency is sacrificed in favor of requesting the bus as quickly as possible. The value in RxDMAUrgentThresh represents free space in the RxFIFO in terms of 32-byte portions. RxDMAU- rgentThresh resets to 4, or a threshold of 128 bytes.

BIT

4..0

7..5

BIT NAME

RxDMAUrgent- Thresh

Unused

BIT DESCRIPTION

The minimum number of 32-byte words which must be available in the RxFIFO to avoid assertion of a RxDMA Urgent Request.

These bits are ignored.

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