VTI Instruments EX1000A - Page 112

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112 EX10xxA Programming
ViInt32 vtb_in;
vtex10xxA_get_vtb_input(vi, &vtb_in);
if (vtb_in & 0x80)
printf(“Bit 7 is high”);
else printf(“Bit 7 is low”);
if (vtb_in & 0x10)
printf(“Bit 4 is high”);
else printf(“Bit 4 is low”);
if (vtb_in & 0x01)
printf(“Bit 0 is high”);
else printf(“Bit 0 is low”);
The vtex10xxA_set_vtb_output function is used to set the static level that each channel of the
trigger bus will assume if/when enabled as an output. Enabling, however, is done with the
vtex10xxA_set_vtb_output_enable function (see below). This function accepts a value that
represents the desired state of the 8-bit bus, specified in either decimal (0 through 255) or hex (0x00
through 0xFF). Within the 8-bit field, the MSB corresponds to VTB channel 7 and the LSB
corresponds to VTB channel 0.
The vtex10xxA_set_vtb_output_enable function enables or disables the output functionality of
each channel of the trigger bus. Once enabled, a channel will assume the level specified with the
vtex10xxA_set_vtb_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 bus, specified in either decimal (0 through 255) or hex (0x00 through 0xFF). Within the 8-bit
field, the MSB corresponds to VTB channel 7 and the LSB corresponds to VTB channel 0.
Example: This code block sets bit 7 (high) and bit 6 (low) of the trigger bus and then enables them
as outputs.
vtex10xxA_set_vtb_output(vi, 0x80);
vtex10xxA_set_vtb_output_enable(vi, 0xC0);
The vtex10xxA_get_vtb_output query is used to obtain the programmed output state of the trigger
bus. The response to this query is a decimal value from 0 to 255 that represents the programmed
output state of the 8-bit bus. However, since the outputs must be enabled, it does not necessarily
represent the true output state. The vtex10xxA_get_vtb_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 bus. Within the 8-bit field, the MSB corresponds to
LXI Trigger Bus (VTB) channel 7 and the LSB corresponds to LXI Trigger Bus (VTB) channel 0.
Example: This code block queries the output state and output enable state of the trigger bus and
reports the states of bit 4.
ViInt32 vtb_out;
ViInt32 vtb_outen;
vtex10xxA_get_vtb_output(vi, &vtb_out);
vtex10xxA_get_vtb_output_enable(vi, &vtb_outen);
if (vtb_out & 0x10)
printf(“Bit 4 is set high”);
else printf(“Bit 4 is set low”);
if (vtb_outen & 0x10)
printf(“Bit 4 is enabled”);
else printf(“Bit 4 is not enabled”);
The vtex10xxA_set_vtb_pulse function is used to generate a 1 s pulse on selected channels of the
trigger bus. The pulse will occur only if the selected channels are enabled as outputs. When a channel
is programmed with a static level of high, the pulse will be low-going. When a channel is