GMAC Network Configuration Register
| 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 | MAXFS | ||||||
| Access | R/W | R/W | R/W | R/W | R/W | ||||
| Reset | 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 |
Speed
Writing a '1' selects 100Mbps operation.
Writing a '0' to this bit selects 10Mbps operation.
Full Duplex
Writing a '1' enables full duplex operation, so the transmit block ignores the state of collision and carrier sense and allows receive while transmitting.
Writing a '0' disables full duplex operation.
Discard Non-VLAN Frames
Writing a '1' to this bit allows only VLAN-tagged frames to pass to the address matching logic.
Writing a '0' to this bit allows both VLAN_tagged and untagged frames to pass to the address matching logic.
Jumbo Frame Size
Writing a '1' to this bit enables jumbo frames of up to 10240 bytes to be accepted. The default length is 10240 bytes.
Copy All Frames
When writing a '1' to this bit, all valid frames will be accepted.
No Broadcast
Writing a '1' to this bit will reject frames addressed to the broadcast address 0xFFFFFFFFFFFF (all '1').
Writing a '0' to this bit allows broadcasting to 0xFFFFFFFFFFFF.
Multicast Hash Enable
When writing a '1' to this bit, 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.
Writing a '0' to this bit disables multicast hashing.
Unicast Hash Enable
When writing a '1' to this bit, 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.
Writing a '0' to this bit disables unicast hashing.
1536 Maximum Frame Size
Writing a '1' to this bit increases the maximum accepted frame size to 1536 bytes in length. When written to '0', any frame above 1518 bytes in length is rejected.
Retry Test
This bit must be written to '0' for normal operation.
When writing a '1' to this bit, the back-off between collisions will always be one slot time. This setting helps testing the too many retries condition. This setting is also useful for pause frame tests by reducing the pause counter's decrement time from "512 bit times" to "every GRXCK cycle".
Pause Enable
When written to '1', transmission will pause if a non-zero 802.3 classic pause frame is received and PFC has not been negotiated.
Receive Buffer Offset
These bits determine the number of bytes by which the received data is offset from the start of the receive buffer.
Length Field Error Frame Discard
Writing a '1' to this bit discards frames with a measured length shorter than the extracted length field (as indicated by bytes 13 and 14 in a non-VLAN tagged frame). This only applies to frames with a length field less than 0x0600.
Remove FCS
Writing this bit to '1' will cause received frames to be written to memory without their frame check sequence (last 4 bytes). The indicated frame length will be reduced by four bytes in this mode.
MDC Clock Division
These bits must be set according to MCK speed, and 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 2.5MHz.
| Value | Name | Description |
|---|---|---|
| 0 | MCK_8 | MCK divided by 8 (MCK up to 20MHz) |
| 1 | MCK_16 | MCK divided by 16 (MCK up to 40MHz) |
| 2 | MCK_32 | MCK divided by 32 (MCK up to 80MHz) |
| 3 | MCK_48 | MCK divided by 48 (MCK up to 120MHz) |
| 4 | MCK_64 | MCK divided by 64 (MCK up to 160MHz) |
| 5 | MCK_96 | MCK divided by 96 (MCK up to 240MHz) |
Data Bus Width
| Value | Name | Description |
|---|---|---|
| 0 | DBW32 |
32-bit data bus width |
| 1 | DBW64 |
64-bit data bus width |
Disable Copy of Pause Frames
Writing a '1' to this bit prevents valid pause frames from being copied to memory. Pause frames are not copied regardless of the state of the Copy All Frames (CAF) 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.
Receive Checksum Offload Enable
Writing a '1' to this bit enables the receive checksum engine, and frames with bad IP, TCP or UDP checksums are discarded.
Enable Frames Received in half-duplex
Writing a '1' to this bit enables frames to be received in half-duplex mode while transmitting.
Ignore RX FCS
For normal operation this bit must be written to zero.
When this bit is written to '1', 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 the DMA descriptor of the frame.
IP Stretch Enable
Writing a '1' to this bit allows the transmit IPG to increase above 96 bit times, depending on the previous frame length using the IPG Stretch Register.
Receive Bad Preamble
When written to '1', frames with non-standard preamble are not rejected.
Ignore IPG GRXER
When this bit is written to '1', the Receive Error signal (GRXER) has no effect on the GMAC operation when Receive Data Valid signal (GRXDV) is low.