dhu(4) - NetBSD Manual Pages

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DHU(4)                NetBSD/vax Kernel Interfaces Manual               DHU(4)

dhu -- DHU-11/DHV-11 serial 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 use ioctl(2) such as ifconfig(8), see tty(4). The DHU-11 driver normally uses input silos and delays receiver inter- rupts by 20 milliseconds rather than taking an interrupt on each input character.
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.
The dhu driver appeared in 4.3BSD. A new dhu driver showed up in NetBSD 1.2.
Even if the dhu hardware supports DMA, the driver cannot make use of this capability. NetBSD 9.0 June 5, 1993 NetBSD 9.0
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