Sundance Spas ST201 - Manual (Page 61)

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Sundance Technology ST201 PRELIMINARY draft 2
TXRELEASETHRESH
Class....................I/O Registers, FIFO Control
Base Address ......IoBaseAddress register value
Address Offset .....0x5d
Access Mode .......Read/Write
Width ...................8 bits
The value in TxReleaseThresh determines how much data of a frame must be transmitted before the
TxFIFO space can be released for use by another frame. Once the number of bytes equal to the value in
TxReleaseThresh have been transmitted, that number of bytes are discarded from the TxFIFO. Thereafter,
bytes are discarded as they are transmitted to the network. TxReleaseThresh resets to 8, i.e., a release
threshold of 128 bytes. A value of 255 in TxReleaseThresh disables the release mechanism and TxFIFO
frame space is not released until the entire frame is transmitted. A TxReleaseError is signaled in TxStatus
when a frame experiences a collision after its release threshold has been crossed, preventing MAC from
retry. When a release error occurs, the transmitter is disabled, and the frame’s ID or sequence number is
visible in TxFrameId.
BIT BIT NAME BIT DESCRIPTION
7..0 TxReleaseThresh The number of 16 byte words which must be transmitted before the
space in the TxFIFO occupied by the transmitted data can be released.
To avoid excessive release errors due to in-window collisions, value
less than 4 should not be written into TxReleaseThresh.