INSTALLATION
2 - 3
Figure 2-4. Connecting TB7 for external power when the control
signals come from a KPCMCIA-PIO24 module.
Then observing polarity, connect the external power supply to the
terminals and -, as shown in Figure 2-4. Note that failure
to observe polarity will blow Fuse F25 and may damage the board.
2.3 PORT DIRECTION SWITCH S1
Parallel I/O cards PIO-12, PIO-24, PIO-96, uPIO-12, and uPIO-24 use an
8255 PPI type interface for communications (information on the 8255
PPI is available from Intel). The 8255 PPI is con
Þ
gured as three ports:
two 8-bit ports (Ports A and B) and one 8-bit port usable as two 4-bit
ports (Port C HI/LOW). Each of these 8255 PPI ports corresponds to a
port on the SSIO-24. Port Direction Switch S1 (see Figure 2-1) selects the
direction of each of these ports.
To set the direction for a port, move the corresponding slide of the Port
Direction Switch to the ON or OFF position. For example, inserting
OUTPUT modules in Ports A and C/LO and INPUT modules in Ports B
and C/HI will require the Port Direction Switch to be set a shown in
Figure 2-5.
Figure 2-5. Setting the Port Direction Switch
