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ZS(4) Device Drivers Manual (macppc) ZS(4)

zs, zstty
Zilog 8530 (ZSCC) serial communications driver

zs* at macobio?
zstty* at zs?

The zs is a Zilog 8530 serial interface chip used in Sun workstations and Apple Macintosh systems. On most newer Macintosh systems, the first port tty00 is connected to the internal modem. The second port is either not connected, or may be connected to an IRDA device (untested). It is possible to replace the internal modem on some system with a real serial port using third party hardware adapters.

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.

/dev/tty00
 
/dev/tty01
 
/dev/cua00
 
/dev/cua01
 

ioctl(2), intro(4), tty(4)

The zs driver first appeared in 4.4BSD. Support for the TIOCM* ioctl(2)s appeared in OpenBSD 2.3.

The zs driver now supports cua minor devices, but with this known deficiency in the simultaneous outgoing/incoming aspect of the driver: The first outgoing connection succeeds, but second and subsequent connections fail, apparently due to a getty hang. The hung getty apparently prevents the cua device from being re-opened.
November 23, 2015 OpenBSD-current