OpenBoot 2.x Command Reference Manual

Input and Output Control

The configuration parameters related to the control of system input and output are:

input-device

output-device

screen-#columns

screen-#rows

ttya-mode

ttyb-mode

You can use these parameters to assign the power-on defaults for input and output and adjust the communication characteristics of the TTYA and TTYB serial ports. Except for the ttya-mode and ttyb-mode results, these values do not take effect until the next power cycle or system reset.

Selecting Input and Output Device Options

The input-device and output-device parameters control the system's selection of input and output devices after a power-on reset. The default input-device value is keyboard and the default output-device value is screen. Input and output can be set to the values in Table 3-3.

Table 3-3 I/O Device Parameters


Options	Description
`device-specifier`	Device identified by that device path name or alias.
`keyboard`	(Input only) Default system keyboard.
`screen`	(Output only) Default graphics display.
`ttya`	Serial port A.
`ttyb`	Serial port B.

When the system is reset, the named device becomes the default input or output device. (If you want to temporarily change the input or output device, use the input or output commands described in Chapter 4, Using Forth Tools.)

To set TTYA as the power-on default input device, type:

ok setenv input-device ttya
ok

If you select keyboard for input-device, and the device is not plugged in, input is accepted from ttya after the next power cycle or system reset. If you select screen for output-device, but no frame buffer is available, output is sent to ttya after the next power cycle or system reset.

To specify an SBus bwtwo frame buffer as the default output device (especially if there are multiple frame buffers in the system), type:

ok setenv output-device /sbus/bwtwo 
ok

Setting Serial Port Characteristics

The default settings for both TTYA and TTYB for most Sun systems are:

9600 baud, 8 data bits, no parity, 1 stop bit, no handshake

The communications characteristics for the two serial ports, TTYA and TTYB, are set using the following values for the ttya-mode and ttyb-mode parameters:

baud = 110, 300, 1200, 2400, 4800, 9600, 19200, or 38400 bits/second
#bits = 5, 6, 7, or 8 (data bits)
parity = n (none), e (even), or o (odd), parity bit
#stop = 1 (1), . (1.5), or 2 (2) stop bits
handshake = - (none), h (hardware (rts/cts)), or s (software (xon/xoff)).

For example, to set TTYA to 1200 baud, seven data bits, even parity, one stop bit, and no handshake, type:

ok setenv ttya-mode 1200,7,e,1,- 
ok

Changes to these parameter values take effect immediately.

Note -

rts/cts and xon/xoff handshaking are not implemented on some systems. When a selected protocol is not implemented, the handshake parameter is accepted but ignored; no messages are displayed.