Chapter 4 Features and Functions

Digital Input OperationsDigital Input Operations

The multifunction module (HP 34907A) has two non-isolated 8-bit input/output ports which you can use for reading digital patterns.

You can read the live status of the bits on the port or you can configure a scan to include a digital read.

∙ The digital input channels are numbered “s01” (lower byte) and “s02”

(upper byte), where s represents the slot number.

 

∙ You can generate an alarm when a specific bit pattern or bit pattern

 

change is detected on an input channel. With the multifunction module,

 

the channels do not have to be part of the scan list to generate an alarm.

 

For more information, see “Using Alarms With the Multifunction Module”

 

on page 130.

 

∙ When you add a digital read to a scan list, that port is dedicated to

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the scan. The instrument issues a Card Reset to make that port an

input port (the other port is not affected). While included in the scan list, you can still perform low-level read operations on the port, but you cannot perform write operations on the port.

∙From the front panel, you can read data from only one 8-bit input port at a time. From the remote interface, you can read both ports simultaneously as a 16-bit word only if neither port is in the scan list. If one or both ports are included in the scan list, you can read only one 8-bit port at a time. However, if you have included both ports in the scan list, the data will be read from both ports simultaneously and will have the same time stamp. Therefore, you can externally combine the two 8-bit quantities into a 16-bit quantity.

∙From the front-panel only, you can specify whether you want to use binary or decimal format (readings are always stored in memory in decimal format). Once you have selected the number base, it is used for all input or output operations on the same port.

∙You can monitor a digital input channel even if the channel is not part of the scan list (the internal DMM is not required either).

∙A Factory Reset (*RST command), Instrument Preset (SYSTem:PRESet command), and Card Reset (SYSTem:CPON command) from the remote interface will reconfigure both ports as input ports.

Note that a from the front panel resets only the port currently selected (both ports are not reset).

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