Data Sheet

Programming Interface — Ethernet Controller I210
407
8.5.4 Flow Control Transmit Timer Value - FCTTV (0x0170; R/W)
The 16-bit value in the TTV field is inserted into a transmitted frame (either XOFF frames or any PAUSE
frame value in any software transmitted packets). It counts in units of slot time of 64 bytes. If software
needs to send an XON frame, it must set TTV to 0x0 prior to initiating the PAUSE frame.
8.5.5 Flow Control Receive Threshold Low - FCRTL0 (0x2160; R/W)
This register contains the receive threshold used to determine when to send an XON packet The
complete register reflects the threshold in units of bytes. The lower four bits must be programmed to
0x0 (16 byte granularity). Software must set XONE to enable the transmission of XON frames. Each
time hardware crosses the receive-high threshold (becoming more full), and then crosses the receive-
low threshold and XONE is enabled (1b), hardware transmits an XON frame. When XONE is set, the RTL
field should be programmed to at least 0x3 (at least 48 bytes).
Flow control reception/transmission are negotiated capabilities by the auto-negotiation process. When
the I210 is manually configured, flow control operation is determined by the CTRL.RFCE and CTRL.TFCE
bits.
8.5.6 Flow Control Receive Threshold High - FCRTH0 (0x2168; R/W)
This register contains the receive threshold used to determine when to send an XOFF packet. The
complete register reflects the threshold in units of bytes. This value must be at maximum 48 bytes less
than the maximum number of bytes allocated to the Receive Packet Buffer (RXPBSIZE.RXPbsize), and
the lower four bits must be programmed to 0x0 (16 byte granularity). The value of RTH should also be
bigger than FCRTL0.RTL. Each time the receive FIFO reaches the fullness indicated by RTH, hardware
transmits a PAUSE frame if the transmission of flow control frames is enabled.
Flow control reception/transmission are negotiated capabilities by the auto-negotiation process. When
the I210 is manually configured, flow control operation is determined by the CTRL.RFCE and CTRL.TFCE
bits.
Field Bit(s) Initial Value Description
TTV 15:0 X Transmit Timer Value.
Reserved 31:16 0x0
Reserved.
Write 0x0, ignore on read.
Field Bit(s) Initial Value Description
Reserved 3:0 0x0
Reserved.
Write 0x0, ignore on read.
RTL 16:4 0x0
Receive Threshold Low.
FIFO low water mark for flow control transmission when transmit flow control is
enabled (CTRL.TFCE = 1b).
An XON packet is sent if the occupied space in the packet buffer is smaller or equal
than this watermark.
This field is in 16 bytes granularity.
Reserved 30:17 0x0
Reserved.
Write 0x0, ignore on read.
XONE 31 0b
XON Enable.
0b = Disabled.
1b = Enabled.