DC(4)

NAME
dc - dc659,dc7085 DZ11-on-a-chip serial communications interface

SYNOPSIS
dc0 at ioasic?
dc0 at mainbus
dc1 at mainbus
dc2 at mainbus
dc0 at vsbus

DESCRIPTION
THe dc driver provides support for Digital's dc7085 four-port serial communcations chip. The dc driver supports dc7085 hardware on attached to the following parent devices:

mainbus
    baseboard device on Decstation 2100, 3100, and 5100, and optional expansion devices on the 5100.
ioasic
    baseboard device on Decstation 5000/200.
vsbus
    baseboard devices on the Vaxstation 2000 and 3100.

The dc device is essentially a single-chip clone of the DZ-11. It has a small input silo shared across all input ports. Model control lines are present on two of the four ports. The device does not interrupt on modem transitions; instead, they are detected via polling. Only two lines on a baseboard dc7085 have modem control signals; the other two are wired for a keyboard and mouse. On some implementations, only partial modem control (sufficent for Unix dialup) is provided, while others provide full modem control. Speeds greater than 19200 are not supported. The 19200 speed is rumoured to actually be 19600, presumably for bug-compatibility with the DZ-11.

HISTORY
The dc driver first appeared in 4.4BSD /pmax. Support for Vax implementations is

BUGS
The Decstation 5000 can set a bit in the system register to allow the dc to run at 38400, but this applies to all four lines and disables the 19200 speed. This feature is not currently supported.

The driver should probably support the original DZ-11, DZ-32, and Qbus DZV-11 and DZQ-11 clones.