ss(4) — VAX
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 4-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 is used; otherwise, the device connected to port 0 is the console.
For the ss device, the flags should always be specified as: flags 0x0f (all 4 lines hardwired). The state of port 2 can 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 can 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.
VAXstation 3100 Communications and Printer Ports
The VAXstation 3100 has two MMJ (Modified Modular Jack) connectors located at the rear of the system box. These MMJ connectors allow connection of terminals, printers, and modems to the VAXstation 3100 system.
The ULTRIX logical names for these connectors are /dev/tty02 (the MMJ closest to the power connector) and /dev/tty03 (the MMJ next to the graphics connector).
Terminals and printers can be connected to either the /dev/tty02 or /dev/tty03 MMJ. Modems can be connected only to the /dev/tty02 MMJ.
The VAXstation 3100 hardware provides only limited modem control support. The DTR (Data Terminal Ready) and DSR (Data Set Ready) signals are the only modem control signals available at the /dev/tty02 MMJ. The ULTRIX device driver for /dev/tty02 has been modified to allow modems to function with the limited modem control provided by the VAXstation 3100. For the modem to function properly, it must be configured to drop DSR when the carrier drops; that is, the modem should not continuously assert DSR.
Restrictions
The speed must be set to 9600 BPS on the console port and 4800 BPS on ports used by graphics devices. The console device must be set for 8-bit character length with one stop bit and no parity. The ss driver enforces these restrictions; 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 then prints a message on the console with interrupts disabled.
Files
/dev/console console terminal or graphics device
/dev/tty00 not used
/dev/tty01 local terminal − multiuser configuration only
/dev/tty02 dialup or local terminal
/dev/tty03 printer port or local terminal
/dev/mouse mouse or tablet − workstation configuration only
/dev/smscreen console message window for monochrome workstations
/dev/sgscreen console message window for color workstations