39.2 GMAC Network Configuration Register

Name: GMAC_NCFGR
Offset: 0x004
Reset: 0x00080000
Property: Read/Write

Bit 3130292827262524 
  IRXERRXBPIPGSEN IRXFCSEFRHDRXCOEN 
Access R/WR/WR/WR/WR/WR/W 
Reset 000000 
Bit 2322212019181716 
 DCPFDBW[1:0]CLK[2:0]RFCSLFERD 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00001000 
Bit 15141312111098 
 RXBUFO[1:0]PENRTY   MAXFS 
Access R/WR/WR/WR/WR/W 
Reset 00000 
Bit 76543210 
 UNIHENMTIHENNBCCAFJFRAMEDNVLANFDSPD 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 

Bit 30 – IRXER Ignore Receive Error from PHY

When set, GRXER has no effect on the GMAC's operation when GRXDV is low.

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).

ValueNameDescription
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 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 10240 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.