Sundance Spas ST201 User Manual
Page 62
62
Sundance Technology
ST201
PRELIMINARY draft 2
TXSTARTTHRESH
Class....................I/O Registers, FIFO Control
Base Address ......IoBaseAddress register value
Address Offset .....0x3c
Access Mode .......Read/Write
Width ...................16 bits
The value in TxStartThresh is used to control when frames are transmitted. Transmission of a frame
begins when the number of bytes for the frame transferred into the TxFIFO is greater than the value in
TxStartThresh
.
If TxStartThresh is set too low, the TxFIFO may experience under run due to the DMA data
transfers not able to keep up with the wire data rate. Host systems should use under run indications as a
hint to increase the TxStartThresh value. This register resets to 1ffch, which disables the threshold mecha-
nism.
BIT
BIT NAME
BIT DESCRIPTION
12..0
TxStartThresh
The number of bytes which must be present in the TxFIFO before
frame transmission begins. Values will be interpreted using a resolu-
tion of 4 bytes (i.e. 0x00, 0x04, 0x08, 0x0c, 0x0f, etc.)
15..13
Unused
These bits are ignored.