EC(4) | Device Drivers Manual (vax) | EC(4) |
ec
— 3Com 10 Mb/s
Ethernet interface
ec0 at uba0 csr 161000 vector ecrint eccollide
ecxint flags 0
NOTE: This driver has not been ported from 4.4BSD yet.
The ec
interface provides access to a 10
Mb/s Ethernet network through a 3Com controller.
The hardware has 32 kilobytes of dual-ported memory on the UNIBUS. This memory is used for internal buffering by the board, and the interface code reads the buffer contents directly through the UNIBUS. The address of this memory is given in the flags field in the configuration file. The first interface normally has its memory at UNIBUS address 0.
Each of the host's network addresses is specified at boot time
with an SIOCSIFADDR
ioctl(2). The
ec
interface employs the address resolution protocol
described in arp(4) to
dynamically map between Internet and Ethernet addresses on the local
network.
The interface software implements an exponential backoff algorithm when notified of a collision on the cable. This algorithm uses a 16-bit mask and the VAX-11's interval timer in calculating a series of random backoff values. The algorithm is as follows:
The ec
driver appeared in
4.2BSD.
The hardware is not capable of talking to itself. The software implements local sending and broadcast by sending such packets to the loop interface. This is a kludge.
Backoff delays are done in a software busy loop. This can degrade the system if the network experiences frequent collisions.
February 5, 2019 | NetBSD 10.99 |