Models 2500 and 2502 User’s Manual Digital I/O Port, Output Enable, and Output Configuration 12-3
Digital output lines
The port provides four output lines and one input line. Each open-collector output can be
set high (+5V) or low (0V). Each output line can source up to 2mA or sink up to 500mA.
When using a category register handler for limit testing, output line #4 is typically used for
the end-of-test (EOT) or BUSY pulse. This pulse from the Model 2500 signals the handler
to perform the binning operation, or indicates a busy condition. (See Section 11, “Config-
uring limit tests.”)
SOT line
The input line (SOT) is used by the handler to start limit testing. With the ↓STEST arm
event selected, the handler must pulse SOT low in order to provide event detection, which
starts the testing process. With the ↑STEST arm event selected, the handler must pulse
SOT high in order to provide event detection and start the testing process. With the
↑↓STEST arm event selected, the handler must pulse SOT either high or low in order to
provide event detection and start the testing process.
EOT/BUSY line
Line 4 can be used for a normal bit pattern, end-of-test (EOT), or BUSY signal, depending
on the selected END OF TEST mode.
NOTE See Section 11 for details on performing limit tests and Section 10 for informa-
tion on programming the Model 2500 to respond to the start-of-test (SOT) pulse
from a handler.
+5V output
The digital I/O port provides a +5V output that can be used to drive external logic cir-
cuitry. Maximum current output for this line is 300mA. This line is protected by a self-
resetting fuse (one hour recovery time).
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