2635A
Users Manual
4-12
PRINT #1, "*RST;FUNC 0,VDC,4;PRINT_TYPE 0,0;PRINT 1;*TRG":PRINT
INPUT$(124, #1)
If other commands are entered, remember that the input character count xxx for
PRINT INPUT$(xxx, #1) command must be exact. A number too small will
not read all the characters and will leave residual characters in the buffer, while a
number too big will "hang up" the command until more characters are loaded into
the buffer or <CNTL><BREAK> is pressed, which erases the buffer.
6. Use Exit to exit QBASIC and return to DOS.
Computer Interface Commands and Operation
Operation of the computer interface between the instrument and PC normally involves
the application software Starter (supplied) and Logger (optional), described in separate
manuals. This chapter is provided for the user who wishes to develop his own software
interface using the instrument command set. The topics in this chapter include:
• How the Instrument Processes Input
• Input Terminators
• Input String Examples
• Sending Numeric Values to the instrument
• How the Instrument Processes Output
• Status Registers
• Computer Interface Command Set

How the Instrument Processes Input

The instrument processes and executes valid input character strings from the host
personal computer (PC). A valid input string is one or more syntactically correct
commands, separated by semicolons (;) followed by an input terminator. The instrument
stores received inputs in a 350-byte buffer. When an input string is received, it is not
executed or checked for proper syntax until the input terminator is received. If the 350-
byte input buffer becomes full, a device-dependent error prompt is returned, and further
inputs to the string are ignored, except for a termination character. The instrument
accepts alphabetic characters in either upper- or lower-case. If a command cannot be
understood, the command and the rest of the command line are ignored.
Commands must be entered in the correct order as follows:
1. Commands to configure the instrument.
2. Commands that trigger a measurement.
3. Commands to read the results of a triggered measurement.
4. Commands to reconfigure the instrument (if any).

Input Terminators

An input terminator is a character sent by the host that identifies the end of a string.
When the input terminator is received, the instrument executes all commands entered
since the last terminator was received, on a first-in, first-out basis. If a communications
error (e.g., parity, framing, overrun) is detected, a device-dependent error is generated.
Valid terminators are LF (line feed), CR (carriage return), CR LF, and LF CR. In some