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).