Remote Processing RPC-330 - Manual (Page 23)

DIGITAL I/O SECTION 6
Page 6-2 RPC -330
maximum of 2. 5 ma at 0.4V and can source over 2. 5
ma. Outputs sink over 15 ma at 1.0V. This will drive
opto modules. Por t B is connected to a high current sink
through U 12. See "H igh curr ent output" later in this
section.
Digital I/O lines at J3 are pulled to + 5 volts or ground
through 10K or 100K resistor packs using jumper W 7.
10K resistor is connected to port A. 100K is connected
t o p o r ts B a n d C .
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 position is
provided. + 5V power and gr ound may be brought in or
taken from this connector.
This por t may be u sed to interfa ce switche s, dr ive small
LED' s, and provide general purpose TTL I/O to other
logic devices. Voltage and current param eters are the
same as J3 except there is no high current output. Port
C from an 82C55 is used for this I/O.
Upon po wer u p or r eset lines L0 to L3 ar e inputs while
L4 to L7 are outputs. Lines L4 and L5 are low while L6
and L7 a re high at p ower up. All lines are connected to
a 10K pull up resistor (R21). Lines are r econfigured for
all inputs or outputs using the CONFIG LINE 0
command, found in Appendix A.
High Current Port L8
L 8 sw i tc h es 2 am p e r es to g r ou n d t hr o u gh a " ze r o oh m "
F E T s w it c h. M a x im u m o ff v ol ta g e i s + 5 0 vo lt s D C .
U s e th is p or t to s wi tc h L ED b a ck li gh ti ng f or L C D
d is pl ay s o n o r of f u n de r so ft w ar e co n tr o l. T h e PW M
comm and is used to control brightness.
This line is always an output. Use the LINE 8 com mand
t o t ur n th is li ne O F F o r O N .
100 LINE 8,ON
The FE T switch is rated for much higher cur rent (> 9
amper es). H owever, continuous curr ent is much less
without a heat sink attached. You may draw m ore than
the rated 2 amps on an intermittent basis. How much
and for how long depends upon your application. A
quick way to check if current is excessive is to touch
(VERY CARE FUL LY!) Q2 (next to P2). It can be
warm to hot to the touch. C onsider the maximum
ambient temperature the board w ill operate at and adding
a heat sink.
Optically Isolated Input
ISOA and ISOB are inputs to an optical isolator. The
output conne cts directly to I NT 0 on P2. When 5 v olts
is applied to ISOA and ISOB, the output goes low.
Refer to SECTION 12 for input voltage and interrupt
requirem ents.
Refer to Using Interrupts as Inputs below for accessing
information through the INT 0 line.
To use the opto isolated input and use INT 0 for counter
interrupts, connect H2-5 to an unused digital input (such
as those at P6). Read the line in a normal manner.
Using Interrupts as Inputs
INT 0 and/ or IN T 1 can be used as an inpu t, inter rupt,
or both provided that its corresponding counter does not
u s e a n in te r r up t. ( C o un te r 0 = I N T 0, c o u nt e r 1 = I N T
1 . ) T o u s e a s an in p ut , j um p e r H 2 ( fo r IN T 0 ) o r H 3
(for INT 1) pins [5-6].
This input is read as:
100 A = LINE(8) : REM INT 0 or isolated
110 B = LINE(9) : REM INT 1
Refer to SECTION 12 for more interr upt information.
Digital I/O Commands
The CON FIG LINE statement is used to configure lines
at J3 and P 6 for inputs a nd outputs. J3 power up default
is all inputs. P6 pow er up de fault is L0 to L 3 are inpu ts
and L4 to L7 are outputs. CONFIG LINE 0 refers to P6
while CON FIG LIN E 100 to J3.
The L INE comm and has 3 vari ations: LIN E, LIN E B,
and LINE #. Each is described below. See Appendix A
for more inform ation.