IOtech Digital488, Manual

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Control Lines
Six control lines enable handshaking of digital I/O data transfer to the Digital488 . They are automatically
activated with the corresponding I/O activity and can be independently activated with the
Handshake (Hn) command. Note that the pin numbers for the Digital488/32/OEM are different from
the pin numbers for the Digital488 .
Clear (Digital488: Pin 41
Digital488/32/OEM: Pin 33)
The Clear output is pulse for approximately 50 microseconds after a Device Clear (DCL), Selected Device
Clear (SDC), or Interface Clear (IFC) command has been sent on the bus. The Clear line is normally active
high. The Invert command ( I8 ) will program it active low. The Handshake command (H0) can pulse the
Clear line, independent of any I/O operations.
Timing Diagram for Clear Output
Data Strobe (Digital488: Pin 42
Digital488/32/OEM: Pin 37)
The Data Strobe output is pulse for approximately 50 microseconds after new data is output on the
I/O port. The Data Strobe line is normally active high but may be programmed active low by the Invert
command ( I4 ). The Handshake command (H1) can pulse the Data Strobe line, independent
of an I/O operation.
Timing Diagram for Strobe Output
Digital488 User’s Manual
11-19-01
Getting Started, 2- 5