UN(4) —

NAME

un − IBM RT PC Baseband Adapter for use with Ethernet

SYNOPSIS

For the IBM RT PC:
device un0 at iocc0 csr 0xf4080000 priority 5
device un1 at iocc0 csr 0xf4088000 priority 4

For the IBM 6152 Academic System:
device un0 at iocc0 csr 0x00001550 priority 3
device un1 at iocc0 csr 0x00001554 priority 3

DESCRIPTION

The un interface provides access to a 10 Mb/s Ethernet network through an IBM RT PC Baseband Adapter for use with Ethernet.

The hardware has 16 kilobytes of dual-ported RAM. Four kilobytes are used for transmit buffers and 12k for receive buffers. The 4k are used to provide two 2k transmit buffers. The hardware permits the processor to fill one buffer while the board is transmitting from the other. The 12k-segment takes the form of 96 128-byte pages. Packets longer than 128 bytes can span multiple pages. The processor and the adapter use two registers to maintain a circular buffer of received packets. The driver writes one register to inform the adapter where the “full” pages start (so that the board doesn’t refill them before the driver empties them). The driver reads the other register to determine where the empty pages start (so that it doesn’t read empty pages before the board fills them). The hardware permits the processor to read from one part of the circular buffer while the board is receiving packets into another part of the buffer.

The host’s Internet address is specified at boot time with an SIOCSIFADDR ioctl. The un interface employs the address resolution protocol described in arp(4P) to map dynamically between Internet and Ethernet addresses on the local network.

The interface supports the “trailer” protocol used by VAXen to minimize byte-shuffling in processing received packets. The use of trailers is negotiated with ARP. This negotiation may be disabled on a per-interface basis by setting the IFF_NOTRAILERS flag with an
SIOCSIFFLAGS ioctl.

WARNING (for the IBM RT PC only): The IBM Ethernet adapter requires dynamic RAM refresh. Do not place the card in slot 5 in the desk-model IBM 6151 Model 10, 15, 115 RT PC, or in slot 8 in the floor-model IBM 6150 Model 20, 25, 125 RT PC; those slots do not provide dynamic RAM refresh.

NOTE

This interface also supports the Ungermann-Bass Personal Computer Network Interface Controller, model number 2274A (PC-NIC card).

The adapter addresses 0xf4090000 and 0xf4098000 are also acceptable default addresses for compatibility with AIX (Advanced Interactive Executive) which uses those addresses. Users expecting to have AIX in co-residence should use those addresses.

DIAGNOSTICS

un%d: huge packet. The hardware detected an illegally large packet and truncated it.

un%d: ethernet jammed. The hardware encountered 16 consecutive collisions in attempting to transmit a packet using the Ethernet exponential backoff algorithm. The packet was dropped. (IBM RT PC only)

un%d: ethernet not responding (is it connected?). The hardware determined that the Ethernet was shorted or disconnected.

un%d: can’t handle af%d. The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped.

Museum