User manual

PCI-1752 User Manual 26
PC, thus when user calls the DRV_DioGet CurrentDOByte ( ) function to
read back the DO channel value, this function will determine that:
• If Channel-Freeze function is disabled, it will return the DO value on
the port;
• If Channel-Freeze function is enabled, it will return the value from the
buffers on host PC.
The PCI-1752U/PCI-1752USO provides a digital input channel
(CH_FRZ_IN) to enable the channel-freeze function. The channel-freeze
function acts when the pin CH_FRZ_IN is activated. Moreover, you can
setup the input mode of channel-freeze function input channel
CH_FRZ_IN as dry contact input mode or wet contact input mode
selected by on-board jumper JP2, as shown in Table 4-3. The wiring in
wet contact and dry contact input mode are shown in Figure 4-2. Other-
wise, you also can enable the function through software by writing “1” to
CFC (Channel-Freeze Function Control) bit on channel-freeze function
register, as shown in Table 4-4 and Table 4-5. It’s useful in software sim-
ulation and testing program.
The CFS (Channel-Freeze Function Status) bit shows the status of Chan-
nel-Freeze function:
A value of 1 for the CFS bit indicates an active Channel-Freeze Function;
whereas a value of 0 indicates a non-active Channel-Freeze Function.
Table 4.3: JP2: Channel-Freeze function input mode
Channel-Freeze function dry contact input mode
Channel-Freeze function wet contact input mode
1
1