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DHU(4) Device Drivers Manual (vax) DHU(4)

dhuDHU-11/DHV-11 communications multiplexer

dhu0 at uba0 csr 0160440

A DHU-11 provides 16 communication lines.

Normal I/O control parameters for individual lines are managed by ioctl(2) calls. Individual DHU-11 lines may be configured to run at any of 13 speeds (50, 200 and 38400 baud are not available); the speed may be set via getty(8) or stty(1) or may be communicated by other programs which utilize ioctl(2) such as ifconfig(8), see tty(4).

The DHU-11 driver normally uses input silos and delays receiver interrupts by 20 milliseconds rather than taking an interrupt on each input character.

/dev/tty[S-Z][0-9a-f]
 

The driver currently does not make full use of the hardware capabilities of the DHU-11, for dealing with XON/XOFF flow-control or hard-wired lines for example.

Although the devices are not the same, a DHU-11 can convince the DH-11 autoconfiguration code that it is a DH-11.

The 4 40-way cables are a pain.

tty(4), uba(4)

The dhu driver appeared in 4.3BSD. A new dhu driver showed up in NetBSD 1.1A.

Even if the dhu hardware supports DMA, the driver cannot make use of this capability.

September 10, 2015 OpenBSD-5.9