Active low oend, Active high oend (default) s3 – Measurement Computing Digital HS User Manual
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on, iRESET, Device Clear (DCL) or Selected Device Clear (SDC). The default setting
for S3-5 is active high. The oEND is not affected by the \OE line; it is always
enabled.
OPEN
8
7
6
5
4
3
2
1
Active Low oEND
OPEN
8
7
6
5
4
3
2
1
Active High oEND
(default)
S3
oEND POL
S3
oEND POL
Polarity Selection for the oEND Control Line
2.2.2.3.6 S3-6 oDATA POL: Output Data Polarity
The output data bits' polarity can be active high or active low. For example, if a data
byte of &h07 is transferred to the output port with oData Polarity selected for active
low operation, the levels at the output port are &hF8.
The first and second byte outport drivers are controlled by the output enable input
(/OE). In order to allow the digital output data to be presented to the output
connector, the /OE input must be forced low. The oEND output is always enabled,
regardless of the state of /OE input. This allows the input and output ports on the
Digital488HS/32 to be connected to form a bi-directional bus.
At power-on, iRESET, Device Clear (DCL) or Selected Device Clear (SDC), S3-6 is
ignored and the 16 data bits of the first and second byte ouput ports are forced to the
levels selected by the S4 and S5 switch settings. These settings are in effect until the
first data are written to the output port. The oEND output is forced active. Default of
S3-6 is active high output data bits.