Electrical Description
The trigger input (-START) line is active low and requires a pulse width of at least 50 ns to activate the
edge-triggered circuitry, which uses 1N4148 diodes to protect against voltages exceeding TTL levels.
Outputs are provided by 7406 inverting buffers, which have open-collector outputs and therefore need
pull-up resistors on the handler for proper operation.
NOTE: The maximum high-level output voltage is 30 V, and the maximum low-level output current is
40 mA. For example, when connecting the output to a 5 V supply at the handler, the pull-up resistors
should be no smaller than 5 V/40 mA = 125 ohms. Flyback diodes should be added if the outputs are
used to drive relay coils, but such a direct connection is not recommended. Ideally, opto-isolators
should be used on all data lines to prevent noise from the handler from interfering with
measurements.
Using Commands
Communications with the Model Z9216 use ASCII characters. Commands may be in either UPPER
or lower case and may contain any number of embedded space characters. A command to the
Model Z9216 consists of a four-character command mnemonic, arguments if necessary, and a
command termination. The terminator may be either a carriage return <CR> or line feed <LF> on
RS232, or a line feed <LF> or EOI on GPIB. No command processing occurs until the meter receives
a command termination. All commands function identically on GPIB and RS232. Commands may
require one or more parameters. Multiple parameters are separated by commas, ",".
Multiple commands may be sent on one command line by separating them by semicolons ";". The
difference between sending several commands on the same line and sending several independent
commands is that when a command line is parsed and executed the entire line is executed before any
other device action proceeds.
There is no need to wait between commands. The Model Z9216 has a 256-character input buffer and
processes commands in the order received. If the buffer fills up, the Model Z9216 will hold off
handshaking on the GPIB and attempt to hold off handshaking on RS232. If the buffer overflows the
buffer will be cleared and an error reported. The GPIB output buffer may be cleared by using the
Device Clear universal command.
The present value of a particular parameter may be determined by querying the Model Z9216 for its
value. A query is formed by appending a question mark "?" to the command mnemonic and omitting
the desired parameter from the command. If multiple queries are sent on one command line
(separated by semicolons, of course) the answers will be returned in a single response line with the
individual responses separated by semicolons. The default response delimiter that the Model Z9216
sends with any answer to a query is carriage return-line feed <CR> <LF> on RS232 and line feed plus
EOI on GPIB, except for binary answers, which are delimited by a line feed signal <LF> on both
interfaces. All commands return integer results except as noted in individual command descriptions.
Example command formats are given in Table 3-5.
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