Data Sheet

Ethernet Controller I210 — Programming Interface
408
8.5.7 Flow Control Refresh Threshold Value - FCRTV (0x2460; R/W)
8.5.8 Flow Control Status - FCSTS0 (0x2464; RO)
This register describes the status of the flow control machine.
Field Bit(s) Initial Value Description
Reserved 3:0 0x0
Reserved.
Write 0x0, ignore on read.
RTH 17:4 0x0
Receive Threshold High.
FIFO high water mark for flow control transmission when transmit flow control is
enabled (CTRL.TFCE = 1b). An XOFF packet is sent if the occupied space in the packet
buffer is bigger or equal than this watermark.
This field is in 16 bytes granularity.
Refer to Section 3.7.5.3.1 for calculation of FCRTH0.RTH value.
Notes:
1. When in DMA coalescing operation and the internal transmit buffer is empty, the
threshold high value defined in FCRTC.RTH_Coal is used instead of the
FCRTH0.RTH value to allow an increase of the receive threshold high value by the
maximum supported Jumbo frame size.
2. The value programmed should be greater than the maximum packet size.
Reserved 31:18 0x0
Reserved.
Write 0x0, ignore on read.
Field Bit(s) Initial Value Description
FC_refresh_th 15:0 0x0
Flow Control Refresh Threshold.
This value indicates the threshold value of the flow control shadow counter when
transmit flow control is enabled (CTRL.TFCE = 1b). When the counter reaches this
value, and the conditions for PAUSE state are still valid (buffer fullness above low
threshold value), a PAUSE (XOFF) frame is sent to link partner.
If this field contains zero value, the flow control refresh is disabled.
Reserved 31:16 X
Reserved.
Write 0x0, ignore on read.
Field Bit(s) Initial Value Description
Flow_control
state
00b
Flow Control State Machine Signal.
0b = XON.
1b = XOFF.
Above high 1 0x0 The size of data in the memory is above the high threshold.
Below low 2 1b The size of data in the memory is below the low threshold.
Reserved 15:3 0x0
Reserved.
Write 0x0, ignore on read.
Refresh
counter
31:16 0x0 Flow Control Refresh Counter.