VTI Instruments EX1000A - Page 105

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EX10xxA Programming 105
Example: This code block queries the state of the I/O port and reports the level of bits 7, 4, and 0.
ViInt32 dio_in;
vtex10xxA_get_dio_input(vi, &dio_in);
if (dio_in & 0x80)
printf(“Bit 7 is high”);
else printf(“Bit 7 is low”);
if (dio_in & 0x10)
printf(“Bit 4 is high”);
else printf(“Bit 4 is low”);
if (dio_in & 0x01)
printf(“Bit 0 is high”);
else printf(“Bit 0 is low”);
The vtex10xxA_set_dio_output function is used to set the static level that each channel of the
digital I/O port will assume if/when enabled as an output. Enabling, however, is done with the
vtex10xxA_set_dio_output_enable function (see below). This function accepts a value that
represents the desired state of the 8-bit port, specified in either decimal (0 through 255) or hex (0x00
through 0xFF). Within the 8-bit field, the MSB corresponds to DIO channel 7 and the LSB
corresponds to DIO channel 0.
The vtex10xxA_set_dio_output_enable function enables or disables the output functionality of
each channel of the digital I/O port. Once enabled, a channel will assume the level specified with
the vtex10xxA_set_dio_output function (see above). When not enabled as an output, a channel
becomes tri-stated. Input functionality on each channel is constant regardless of its output
functionality. This function accepts a value that represents the desired output enable state of the 8-
bit port, specified in either decimal (0 through 255) or hex (0x00 through 0xFF). Within the 8-bit
field, the MSB corresponds to DIO channel 7 and the LSB corresponds to DIO channel 0.
Example: This code block sets bit 7 (high) and bit 6 (low) of the I/O port and then enables them as
outputs.
vtex10xxA_set_dio_output(vi, 0x80);
vtex10xxA_set_dio_output_enable(vi, 0xC0);
The vtex10xxA_get_dio_output query is used to obtain the programmed output state of the DIO
channels. The response to this query is a decimal value from 0 to 255 that represents the programmed
output state of the 8-bit port. However, since the outputs must be enabled, it does not necessarily
represent the true output state. The vtex10xxA_get_dio_output_enable query is used to obtain the
output enable state of each channel. The response to this query is a decimal value from 0 to 255 that
represents the output enable state of the 8-bit port. Within the 8-bit field, the MSB corresponds to
DIO channel 7 and the LSB corresponds to DIO channel 0.
Example: This code block queries the output state and output enable state of the I/O port and reports
the states of bit 4.
ViInt32 dio_out;
ViInt32 dio_outen;
vtex10xxA_get_dio_output(vi, &dio_out);
vtex10xxA_get_dio_output_enable(vi, &dio_outen);
if (dio_out & 0x10)
printf(“Bit 4 is set high”);
else printf(“Bit 4 is set low”);
if (dio_outen & 0x10)
printf(“Bit 4 is enabled”);
else printf(“Bit 4 is not enabled”);