Astronics RACAL INSTRUMENTS 1260-164AH, Manual, Page: 25 / 28

Publication No. 980824-164AH/BH Rev. A 1260-164AH/BH User Manual
Astronics Test Systems Module Operation 3-5
Table 3-5, EPROM Descriptor Functionality of the 1260-164 Module
Register Table
EPROM Descriptor Register
Module Version Bit Functionality Description
All
0 Each time this register is read, it advances a memory pointer to
the next memory location in the on-board EPROM. To reset this
pointer to the beginning, read the ID register. This resets the
memory pointer. The descriptor register contains a long string of
data, typically used by the Adapt-a-Switch carrier for configuration
purposes. Additionally, this data contains the card identification
string for the specific type of card (i.e. 1260-164AH or 1260-
164BH). These identification strings are located at EPROM
memory locations 0x23 through 0x34.
1
2
3
4
5
6
7
Writing to a port location is a straightforward process. Setting a bit
high in a port register causes the corresponding relay channel to
close.
It is especially important to realize that a single write operation
controls eight separate control lines or output devices
simultaneously. Therefore if only a single bit change is desired, the
following process must be observed.
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 1260-164 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 1260-164 module.