8.2.2 GMAC Network Configuration Register
| Name: | GMAC_NCFGR |
| Offset: | 0x004 |
| Reset: | 0x00080000 |
| Property: | Read/Write |
| Bit | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | |
| IRXER | RXBP | IPGSEN | IRXFCS | EFRHD | RXCOEN | ||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | |||
| Reset | 0 | 0 | 0 | 0 | 0 | 0 |
| Bit | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | |
| DCPF | DBW[1:0] | CLK[2:0] | RFCS | LFERD | |||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | |
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| RXBUFO[1:0] | PEN | RTY | GBE | MAXFS | |||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | |||
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | |||
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| UNIHEN | MTIHEN | NBC | CAF | JFRAME | DNVLAN | FD | SPD | ||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Bit 30 – IRXER Ignore Receive Error from PHY
When set, GRXER has no effect on the GMAC's operation when GRXDV is low. Set this bit when using the RGMII wrapper in Half Duplex mode.
Bit 29 – RXBP Receive Bad Preamble
When set, frames with non-standard preamble are not rejected.
Bit 28 – IPGSEN IP Stretch Enable
When set, the transmit IPG can be increased above 96 bit times depending on the previous frame length using the IPG Stretch Register.
Bit 26 – IRXFCS Ignore RX FCS
When set, frames with FCS/CRC errors will not be rejected. FCS error statistics will still be collected for frames with bad FCS and FCS status will be recorded in frame’s DMA descriptor. For normal operation this bit must be set to zero.
Bit 25 – EFRHD Enable Frames Received in Half Duplex
Enable frames to be received in half-duplex mode while transmitting.
Bit 24 – RXCOEN Receive Checksum Offload Enable
When set, the receive checksum engine is enabled. Frames with bad IP, TCP or UDP checksums are discarded.
Bit 23 – DCPF Disable Copy of Pause Frames
Set to one to prevent valid pause frames being copied to memory. When set, pause frames are not copied to memory regardless of the state of the Copy All Frames bit, whether a hash match is found or whether a type ID match is identified. If a destination address match is found, the pause frame will be copied to memory. Note that valid pause frames received will still increment pause statistics and pause the transmission of frames as required.
Bits 22:21 – DBW[1:0] Data Bus Width
Must always be written to ‘0’.
Bits 20:18 – CLK[2:0] MDC Clock Division
Set according to MCK speed. These three bits determine the number MCK will be divided by to generate Management Data Clock (MDC). For conformance with the 802.3 specification, MDC must not exceed 2.5 MHz (MDC is only active during MDIO read and write operations).
| Value | Name | Description |
|---|---|---|
| 0 | MCK_8 | MCK divided by 8 (MCK up to 20 MHz) |
| 1 | MCK_16 | MCK divided by 16 (MCK up to 40 MHz) |
| 2 | MCK_32 | MCK divided by 32 (MCK up to 80 MHz) |
| 3 | MCK_48 | MCK divided by 48 (MCK up to 120 MHz) |
| 4 | MCK_64 | MCK divided by 64 (MCK up to 160 MHz) |
| 5 | MCK_96 | MCK divided by 96 (MCK up to 240 MHz) |
Bit 17 – RFCS Remove FCS
Setting this bit will cause received frames to be written to memory without their frame check sequence (last 4 bytes). The frame length indicated will be reduced by four bytes in this mode.
Bit 16 – LFERD Length Field Error Frame Discard
Setting this bit causes frames with a measured length shorter than the extracted length field (as indicated by bytes 13 and 14 in a non-VLAN tagged frame) to be discarded. This only applies to frames with a length field less than 0x0600.
Bits 15:14 – RXBUFO[1:0] Receive Buffer Offset
Indicates the number of bytes by which the received data is offset from the start of the receive buffer
Bit 13 – PEN Pause Enable
When set, transmission will pause if a non-zero 802.3 classic pause frame is received and PFC has not been negotiated.
Bit 12 – RTY Retry Test
Must be set to zero for normal operation. If set to one the backoff between collisions will always be one slot time. Setting this bit to one helps test the too many retries condition. Also used in the pause frame tests to reduce the pause counter's decrement time from 512 bit times, to every GRXCK cycle.
Bit 10 – GBE Gigabit Mode Enable
Setting this bit configures the GMAC for 1000 Mbps operation.
| Value | Description |
|---|---|
| 0 |
10/100 operation. |
| 1 |
Gigabit operation. |
Bit 8 – MAXFS 1536 Maximum Frame Size
Setting this bit means the GMAC will accept frames up to 1536 bytes in length. Normally the GMAC would reject any frame above 1518 bytes.
Bit 7 – UNIHEN Unicast Hash Enable
When set, unicast frames will be accepted when the 6-bit hash function of the destination address points to a bit that is set in the Hash Register.
Bit 6 – MTIHEN Multicast Hash Enable
When set, multicast frames will be accepted when the 6-bit hash function of the destination address points to a bit that is set in the Hash Register.
Bit 5 – NBC No Broadcast
When set to logic one, frames addressed to the broadcast address of all ones will not be accepted.
Bit 4 – CAF Copy All Frames
When set to logic one, all valid frames will be accepted.
Bit 3 – JFRAME Jumbo Frame Size
Set to one to enable jumbo frames up to 16383 bytes to be accepted. The default length is 10240 bytes.
Bit 2 – DNVLAN Discard Non-VLAN FRAMES
When set, only VLAN tagged frames will be passed to the address matching logic.
Bit 1 – FD Full Duplex
If set to logic one, the transmit block ignores the state of collision and carrier sense and allows receive while transmitting.
Bit 0 – SPD Speed
Set to logic one to indicate 100 Mbps operation, logic zero for 10 Mbps.