Data Sheet

Ethernet Controller I210 — Programming Interface
544
8.25.6 Flow Control Receive Threshold Coalescing - FCRTC (0x2170; R/
W)
8.25.7 DMA OBFF Control Register - DOBFFCTL (0x3F24;Rw)
8.25.8 DMA Coalescing Clock Control Time Counter - DMACTC (0x5DC8;
RO)
This register keeps track of the number of time units elapsed since the end of last time interval.
Field Bit(s) Initial Value Description
Reserved 3:0 0x0
Reserved.
Write 0x0 ignore on read.
RTH_Coal 17:4 0x0
Flow control receive threshold high watermark value used to generate a XOFF flow
control packet when executing DMA coalescing, internal transmit FIFO is empty and
transmit flow control is enabled (CTRL.TFCE = 1b). When previous conditions exist, a
XOFF packet is sent if the occupied space in the Rx packet buffer is more or equal to
this watermark.
This field is in 16 bytes granularity.
Refer to Section 3.7.5.3.1to calculate the FCRTC.RTH_Coal value.
Notes:
1. To avoid sending XOFF flow control packets needlessly when executing DMA
coalescing and the internal transmit buffer is empty, the value should be higher
than the threshold defined in the DMACR.DMACTHR field. Maximum threshold
value can be up to FCRTH0.RTH + maximum allowable packet size * 1.25.
2. RTH_Coal threshold value is used as a watermark for sending flow control
packets when DMA coalescing is enabled and the internal transmit buffer is
empty.
3. The value programmed should be greater than the maximum packet size.
Reserved 31:18 0x0
Reserved
Write 0 ignore on read.
Field Bit(s) Initial Value Description
OBFFTHR 7:0 0x0
DMA OBFF Threshold.
Defines the low threshold that the Rx buffer needs to pass to initiate a new transaction
when in OBFF mode. It is expressed in KB units.
IDLTO 15:8 0x20
Idle Timeout.
Defines the amount of idle cycles before starting coalescing entry flow
ACTTO 23:16 0x02
Active Timeout.
Defines the amount of non-idle cycles before stopping coalescing entry flow
Reserved 31:24 0x0 Reserved.
Field Bit(s) Initial Value Description
COUNT 9:0 0x0
SC Time Counter.
The counter for the number of time units elapsed since the end of the last time
interval.
RSVD 31:10 0x0 Reserved.