6-10 Automating Measurements
Controlling Peripherals
Hardcopy Considerations
Hardcopy Considerations
The analyzer's feature can send output to printers
connected to the parallel port. If you have a custom interface circuit
attached to the parallel port, you don't want the hardcopy output to
interfere with it.
To address this issue, the analyzer uses the parallel port's printer-select
signal (pin 17) to differentiate between hardcopy dumps and user-issued
WRITEIO and DIAG:PORT:WRITe commands. During a hardcopy to the
parallel port, the printer-select signal is driven low. During WRITEIO and
DIAG:PORT:WRITe commands, it is driven high.
Using the printer-select signal, you can connect both an interface circuit
and a printer to the parallel port. The interface circuit should only
respond to the data strobe (pin 1) when the printer-select signal is high.
The printer should only respond to the data strobe when the
printer-select signal is low. Most printers require the printer-select line
to be low, or else they will not print. Some printers ignore this line. If you
are using a printer which ignores this line you have two choices:
1. Consult the printer’s manual to see if there is a DIP-switch setting
that controls how the printer responds to the printer-select signal, or
if not,
2. Design your interface circuit so that it gates and inhibits the data
strobe signal (pin 1) going to the printer when printer-select is high.
Similar to the output signals, you can use the printer-select signal to
multiplex the input signals, selecting either the signals from your
interface circuit or those from the printer.
HARDCOPY
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