am79c940 Advanced Micro Devices, am79c940 Datasheet - Page 76

• Manufacturer Part Number: am79c940
• Description: Media Access Controller For Ethernet Mace
• Manufacturer: Advanced Micro Devices

Programmer’s Register Model
76
Addr
0
1
2
3
4
5
6
7
8
AMD
Mnemonic
RCVFIFO
XMTFIFO
FIFOFC
XMTRC
XMTFC
XMTFS
RCVFC
RCVFS
IR
Receive FIFO—16 bits
Transmit FIFO—16 bits
Transmit Frame Control
80
08
01
Transmit Frame Status
80
40
20
10
08
04
02
01
80
40
20
10
0F
Receive Frame Control
08
04
01
Receive Frame Status—4 bytes—read in 4 read cycles
RFS0
RFS1
RFS2
RFS3
FIFO Frame Count
F0
0F
Interrupt Register
80
40
20
10
08
04
02
01
DRTRY
DXMTFCS
APADXMT
XMTSV
UFLO
LCOL
MORE
ONE
DEFER
LCAR
RTRY
EXDEF
—
—
—
XMTRC [3:0] 4-bit Transmit Retry Count
LLRCV
M/R
ASTRPRCV
RCVCNT [7:0] Receive Message Byte Count
RCVSTS, RCVCNT [11:8]—Receive Status & Receive Msg Byte Count MSBs
80
40
20
10
0F
RNTPC [7:0]
RCVCC [7:0] Receive Collision Count (since last successful reception)
RCVFC
XMTFC
JAB
BABL
CERR
RCVCCO
RNTPCO
MPCO
RCVINT
XMTINT
Disable Retry
Disable Transmit FCS
Auto Pad Transmit
Transmit Status Valid
Underflow
Late Collision
MORE than one retry was needed
Exactly ONE retry occurred
Transmission was deferred
Loss of Carrier
Transmit aborted after 16 attempts
Excessive Defer
Low Latency Receive
Match/Reject for external address detection
Auto Strip Receive—Strips pad and FCS from received frames
OFLO
CLSN
FRAM
FCS
RCVCNT [11:8]
Runt Packet Count (since last successful reception)
Receive Frame Count—# of RCV frames in FIFO
Transmit Frame Count—# of XMT frames in FIFO
Jabber Error—Excessive transmit duration (20–150ms)
Babble Error 1518 bytes transmitted
Collision Error—No SQE Test Message
Receive Collision Count Overflow—Reg Addr 27 overflow
Runt Packet Count Overflow—Reg Addr 26 overflow
Missed Packet Count Overflow—Reg Addr 24 overflow
Receive Interrupt—Host has read last byte of packet
Transmit Interrupt—Transmission is complete
Am79C940
Contents
Receive FIFO Overflow
Collision during reception
Framing Error
FCS (CRC) error
4 MSBs of Receive Msg. Byte Count
R/W
R/W
R/W
WO
RO
RO
RO
RO
RO
RO
RO