
CD2231 — Intelligent Two-Channel LAN and WAN Communications Controller
148
Datasheet
B Transmit Buffer Status (BTBSTS) — Async-HDLC/PPP Mode
Bit 7
Berr – Bus error (set by the CD2231, and cleared by the host)
0 = No bus error
1 = Bus error was detected on the last transfer
Bit 6
EOF – End of frame (set and cleared by the host)
0 = This buffer is not the last in frame/block.
1 = This buffer is the last in frame/block.
Bit 5
EOB – The end of a transmit buffer (set by the CD2231, and cleared by the host).
The end of a host supplied transmit buffer has been reached.
Bits 4:3
Reserved – must be ‘0’.
Bit 2
map32 – Map all transmit characters from 00–1F (set and cleared by the host)
0 = Use the normal TXACCM map.
1 = Map all characters in the range from 00–1F.
Bit 1
INTR – Interrupt
0 = No interrupt required after the buffer is transmitted.
1 = Interrupt required after the buffer is transmitted.
Bit 0
2231own – Ownership of the transmit buffer (set by the host and cleared by the
CD2231)
0 = Buffer is owned by the host, and not ready for use by the CD2231.
1 = Buffer is owned by the CD2231, and is ready for use by the CD2231.
To start transmission of a buffer, the host must set the ATBADR/BTBADR (Transmit Buffer
Address) and ATBCNT/BTBCNT (Transmit Buffer Count) registers, and then set the 2231own bit.
If the CD2231 is to generate and send the CRC for the frame, the CRC bit in COR1 must be set. If
the buffer contains the end of a frame, the EOF bit must also be set. When the buffer has been sent,
the EOB bit is set by the CD2231, and 2231own is reset, allowing a new buffer to be allocated.
8.6.5.8
A Transmit Buffer Status (ATBSTS) — SLIP/MNP4 Mode
Register Name: BTBSTS
Register Description: Transmit Buffer ‘B’ Status
Default Value: x’00
Access: Byte Read/Write
Intel Hex Address: x’5D
Motorola Hex Address: x’5E
Bit 7Bit 6Bit 5Bit 4Bit 3
Bit 2Bit 1
Bit 0
Berr
EOF
EOB
0
map32
INTR
2231own
Register Name: ATBSTS
Register Description: Transmit Buffer ‘A’ Status
Default Value: x’00
Access: Byte Read/Write
Intel Hex Address: x’5C
Motorola Hex Address: x’5F
Bit 7Bit 6Bit 5
Bit 4
Bit 3Bit 2Bit 1Bit 0
Berr
EOF
EOB
0
INTR
2231own