ZS(4)

NAME
zs, zskbd, zsms, zstty - Zilog 8530 (ZSCC) Serial Communications Controller

SYNOPSIS
zs0 at hpc0
zs1 at hpc0
zskbd* at zs1 channel 0 (Indigo)
zsms* at zs1 channel 1 (Indigo)
zstty* at zs0 channel ?

DESCRIPTION
The zs driver provides TTY support for Zilog 8530 Dual UART chips. On Indigo systems, one of the interfaces is hardwired for use by the keyboard and mouse. The zskbd devices connect keyboard devices to the generic keyboard driver wskbd. The zsms devices connect mice to the generic mouse driver wsmouse(4). The remaining additional zstty interfaces provide RS-423 and RS-232 serial ports for general purpose use.

The zs driver supports all of the standard tty(4) ioctl calls. The status of the DTR, RTS, CTS, and DCD signals can be queried with TIOCMGET command, but, due to limitations in the hardware, only the DTR and RTS signals can be modified with TIOCMSET, TIOCMBIC, and TIOCMBIS ioctl(2) commands.

Input and output for each line may set to any baud rate in the range 50 to 38400 (and higher on some machines).

On some systems, the hardware design causes the state of the CTS, DCD, DTR and RTS lines to be inverted. While the zstty driver attempts to correctly account for this quirk, it can be forced to reverse its logic by setting flags to 1 (either via config(8) or boot_config(8)). Misconfiguration of these line settings usually leads to getty(8) processes being unable to open the device or sleeping on ‘ttyopn’.

FILES
/dev/ttya
/dev/ttyb

DIAGNOSTICS

zs0*: fifo overflow
    The on-chip “FIFO” has overflowed and incoming data has been lost. This generally means the machine is not responding to interrupts from the ZS chip fast enough, which can be remedied only by using a lower baud rate.

zs0*: ring overflow
    The software input "ring" has overflowed. This usually means input flow-control is not configured correctly (i.e. incorrect cable wiring).

SEE ALSO
hpc(4), intro(4), tty(4), wskbd(4), wsmouse(4)