Data Sheet

Ethernet Controller I210 — Programming Interface
542
8.25.2 DMA Coalescing Transmit Threshold - DMCTXTH (0x3550;RW)
EXIT_DC (SC) 25 0b
Exit DMA Coalescing.
Software can initiate a one time move out of the DMA coalescing state by setting this
bit to 1b.
OBFF_STATUS
(RO)
27:26 00b
OBFF Status.
This field reflects the OBFF status as decoded by the PCIe:
00b = OBFF_DISABLE, OBFF is disabled.
01b = OBFF_ACTIVE, OBFF active mode - no coalescing done.
10b = OBFF_IDLE, OBFF idle mode - do not transmit anything.
11b = OBFF_OBFF, OBFF mode - transmit data, but no interrupts.
Reserved 29:28 11b
Reserved.
Write 11b, ignore on read.
Reserved 30 0b
Reserved.
Write 0b, ignore on read.
DMAC_EN 31 0b
DMA Coalescing Enable.
0b = Disable DMA Coalescing.
1b = Enable DMA Coalescing.
Field Bit(s) Initial Value Description
DMCTTHR 11:0 0xE4
DMA Coalescing Transmit Threshold.
This value defines the DMA coalescing transmit threshold in 64 byte units. When the
amount of empty space in the internal transmit buffer exceeds the DMCTTHR value
and additional transmit data is available in main memory, DMA coalescing is stopped
and PCIe moves to an L0 state.
Notes:
1. If this value is 0x0 or smaller than the maximum transmit packet size, as defined
in the DTXMXPKTSZ.MAX_TPKT_SIZE field, a condition to move out of DMA
coalescing due to the passing of the DMA coalescing transmit threshold level is
disabled.
2. The transmit threshold size should be smaller than the internal transmit buffer
area reported in the TXPBSIZE field.
Reserved 31:12 0b
Reserved.
Write 0x0, ignore on read.
Field Bit(s) Initial Value Description