DIGITAL AND OPTO PORTS SECTION 6
Page 6-2 RPC-320
ground through a 10K/100K resistor packs using jumper
W7. 10K is on digital port A only.
Jumper W7 for pull up or down configuration is as
follows:
W7[1-2] Pull up
W7[2-3] Pull down
Setting W7 for pull up makes interfacing to switches and
"open collector" TTL devices easy. See "Inter facing to
Switches and other devices" below.
Digital Port P6
Connector P6 has 8 digital I/O lines for general pur pose
use. Additionally, 3 ground and a + 5V positions are
provided. + 5V power and ground may be brought in or
taken from this connector. Lines are numbered L0-L7.
This port may be used to interface switches, dr ive small
LED' s, and provide general purpose TTL I/O to other
logic devices. Voltage and current parameters are the
same as J3 except there is no high current output. Port
C from an 82C55 is used for this I/O.
Upon power up or reset lines L0 to L3 are inputs while
L4 to L7 are outputs. Lines L4 and L5 are low while L6
and L7 are high at power up. All lines are connected to
a 10K pull up resistor (R21). Lines are reconfigured for
all inputs or outputs using the CONFIG LINE 0
command, found in Appendix A.
High Current Port L8
L8 will switch 2 amperes to ground through a "zero
ohm" FET switch. Maximum off voltage is + 50 volts
DC. "ON" resistance is about 0.5 ohm.
Use this port to switch LED back lighting for LCD
displays on or off under softwar e control.
This line is always an output. Use the LINE 8 command
to turn this line off or on.
LINE 8,ON
LINE 8,1 Both commands turn on L8.
The FET sw itch is rated for much higher current.
However, continuous current is much less without a heat
sink attached. You may draw more than the rated 2
amps on an intermittent basis. How m uch and for how
long depends upon your application. A quick way to
check for excessive current is to touch (VERY
CAREFUL LY!) Q2 (next to P2). It can be warm to hot
to the touch. Consider the maximum ambient
temperature the board w ill operate at. At 70°C, warm to
the touch at room temperature may be too much.
Consider adding a heat sink.
The PW M command may be used with this port. Use
the circuit in Figure 6-2 when switching inductive loads.
Use the "GND" terminal next to L8 when switching
loads.
Optically Isolated Input
ISOA and ISOB are inputs to an optica l isolator. This
input is read as L8. It can also generate an interrupt
provided W8[1-2] is jumpered and ONITR is set. Refer
to Chapter 12 for input voltage and interrupt
requirements. This line can be used to "wake up" the
CPU from low power IDLE 2 mode.
The status is read using the LINE(8) function.
A = LINE(8)
A 1 is returned when there is no input and a 0 when
voltage is sufficiently high enough to turn on the isolator
(about 3.5 volts).
The opto isolator is not polarity sensitive. This input can
be used in conjunction with or independently of the
ONIT R statement.
Digital I/O Commands
The CONFIG LINE statement is used to configure lines
at J3 and P6 for inputs and outputs. J3 power up default
is all inputs. P6 power up default is L0 to L3 are inputs
and L4 to L7 are outputs. CONFIG LINE 0 refers to P6
while CONFIG LINE 100 to J3.
The L INE command has 3 variations: LINE, LIN E B,
and LINE #. Each is described below. See Appendix A
for more inform ation.
LINE function and statement is used with M PS-XX opto
rack at J3. It accesses a module according to the
position number printed on the MPS board. Lines are
numbered from 100 to 123. The opto module number
used in this command is computed by adding 100 to the
board position number. LINE also accesses L0-L8 on
P2 and P6.
The LIN E B function and statement is used to access
