NAME

ss − Small VAX serial line interface

SYNTAX

device ss0 at uba0 csr 0x200a0000 flags 0x0f

vector ssrint ssxint

DESCRIPTION

The Small VAX serial line controller is similar to the DZQ11 four-line communications multiplexer.  An ss interface provides four communication ports with partial modem control on port 2, adequate for dialup use. Only port 2 supports modem control (dialup access). All other ports must be operated as local lines. Each line attached to the serial line controller behaves as described in tty() and may be set to run at any of 16 speeds. For the encoding, see tty(.). However, configuration requirements dictate fixed speed operation of ports connected to the console terminal and graphics devices.

The Small VAX may be configured as a workstation or a multiuser timesharing system.  For the workstation configuration, the ss ports are used as follows:

Port      Usage
0         Graphics device keyboard at 4800 BPS
1         Mouse or tablet at 4800 BPS
2         Communications (with modem control)/local terminal
3         Serial printer port

For the multiuser configuration, the ss port usage is:

Port      Usage
0         Console terminal at 9600 BPS
1         Local terminal line
2         Communications (with modem control)/local terminal
3         Local terminal or serial printer

For either configuration, a diagnostic console terminal may be connected to port 3 using a BCC08 cable.  For the multiuser configuration, while the diagnostic console is connected, no other terminal devices can be connected.  When the diagnostic console is in use, the processor may be halted by pressing the BREAK key. 

The selection of which port to use for the console is made during the processor’s power on sequence and cannot be changed after power on.  If the diagnostic console is connected, it will be used; otherwise the device connected to port 0 will be the console. 

For the ss device, the flags should always be specified as: flags 0x0f (all 4 lines hardwired). The state of port 2 may be established by specifying either modem or nomodem as part of the /etc/ttys file entry for tty02; see ttys(.). The default state of port 2 may be controlled by flags bit 2. Set ‘flags 0x0f’ for a hardwired line, ‘flags 0x0b’ for dialup operation (wait for carrier).

The ss driver operates in interrupt-per-character mode (all pending characters are flushed from the silo on each interrupt). Silo alarm mode is used by the DZQ11 driver at times of high input character traffic.  This mode is not used by the ss driver, due to the need to track mouse or tablet position changes in real time.

RESTRICTIONS

Speed must be set to 9600 BPS on the console port and 4800 BPS on ports used by graphics devices.  The ss driver enforces this restriction; that is, changing speeds with the stty command may not always work on these ports. 

DIAGNOSTICS

ss0: input silo overflow.  The 64-character input silo overflowed before it could be serviced.  This can happen if a hard error occurs when the CPU is running with elevated priority, as the system will then print a message on the console with interrupts disabled. 

FILES

/dev/consoleconsole terminal or graphics device
/dev/tty00not used
/dev/tty01local terminal - multiuser configuration only
/dev/tty02dialup or local terminal
/dev/tty03printer port or local terminal
/dev/mousemouse or tablet - workstation configuration only
/dev/smscreenconsole message window for workstations

SEE ALSO

console(4), devio(4), sm(4), tty(4), ttys(5), MAKEDEV(8)

Special Files