DIGITAL AND OPTO PORTS
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:
Pull up | |
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 gr ound may be brought in or taken from this connector. L ines are numbered L
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
L8 will switch 2 amperes to ground through a "zero ohm" FET switch. Maxim um off vo ltage 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 com mand to turn this line off or on.
LINE 8,ON
LINE 8,1 Both commands turn on L8.
The F ET sw itch is rated fo r mu ch higher curr ent. However, continuous current is much less without a heat sink attached. You may dr aw more than the rated 2 amps on an intermittent basis. How m uch and for how long depend s upon your application. A quick w ay to check for excessive current is to touch (VERY
CARE FUL LY!) Q2 (next to P2). It can be warm to hot
SECTION 6
to the touch. Consider the maxim um ambient
temper ature the b oard w ill operate a t. A t 70°C, warm to the touch at room temperature m ay be too much. Consider adding a heat sink.
The PW M com mand m ay be used with this port. Use the circuit in Figur e
Optically Isolated Input
ISOA a nd ISOB ar e inputs to an optica l isolator. This input is read as L8. It can also generate an interrupt provided
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 statem ent.
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.
LIN E function and statem ent is used with M
The LIN E B function and statement is used to acc ess
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