Racal Instruments 1260-X121 User Manual page 29

1260-X121 User Manual
Racal Instruments © 2005
1. Read the register, inverting the bit pattern.
2. Mask the appropriate bit with an 'AND' operation and a byte
mask with all undesired bits set to a '1' and the desired bit set
to a '0' or '1' depending on whether the bit is to be set or
cleared in the desired register.
3. Write the masked data back into the register.
As simple as this may seem, a number of products reported as
faulty and sent back for repair are typically the result of
inappropriate register accesses.
Because of the 1260-X121 relay driver architecture, registers A
and B will read back inverted from what was written to them.
The VISA I/O library may be used to control the module. The VISA
function viOut8() is used to write a single 8-bit byte to a control
register, while viIn8() is used to read a single 8-bit byte from the
control register. The following code example shows the use of
viOut8() to update the 1260-X121 module.
Module Operation 3-7