HP VXI 75000 C Series, User'S And Scpi Programming Manual

Page: 118 / 438

118 Creating and Running Custom Algorithms Chapter 4
Accessing I/O
Channels
In the Algorithm Language, channels are referenced as pre-defined variable
identifiers. The general channel identifier syntax is "Iccc" for input channels
and "Occc" for output channels; where ccc is a channel number from 100
(channel 0) through 163 (channel 63). Like all HP E1415 variables, channel
identifier variables always contain 32-bit floating point values even when
the channel is part of a digital I/O SCP. If the digital I/O SCP has 8-bit
channels (like the HP E1533), the channel’s identifiers (Occc and Iccc) can
take on the values 0 through 255. To access individual bit values you may
append ".Bn" to the normal channel syntax; where n is the bit number (0
through 7). If the Digital I/O SCP has single-bit channels (like the
HP E1534), its channel identifiers can only take on the values 0 and 1.
Examples:
O100 = 1;
assign value to output chan 0 on
HP E1534.
Inp_val = I108;
from 8-bit channel on HP E1533
Inp_val will be 0. to 255.
Bit_4 = I109.B4;
assign HP E1533 chan 9 bit 4 to
variable Bit_4
Output Channels
Output channels can appear on either or both sides of an assignment
operator. They can appear anywhere other variables can appear. Examples:
O100 = 12.5;
send value to output channel
buffer element 0
O108.B4 = ! O108.B4;
compliment value found in
output channel buffer element 8,
bit 4 each time algorithm is
executed.
writecvt(O116,350);
send value of output channel 16
to CVT element 350
Input Channels
Input channel identifiers can only appear on the right side of assignment
operators. It doesn’t make sense to output values to an input channel. Other
than that, they can appear anywhere other variables can appear. Examples:
dig_bit_value = I108.B0; retrieve value from Input
Channel Buffer element 8, bit 0
inp_value = I124;
retrieve value from Input
Channel Buffer element 24
O156 = 4 * I124; retrieve value from Input
Channel Buffer element 24,
multiply by 4 and send result to
Output Channel Buffer element
56
writefifo(I124);
send value of input channel 24 to
FIFO buffer
Defined Input and Output
Channels
Your algorithm "references" channels. It can reference input or output
channels. But, in order for these channels to be available to your algorithm
they must be "defined". What we mean by "defined" is that an SCP must be
installed, and an appropriate SOURce or SENSe :FUNCtion must explicitly