|
LIBRARY
OF
ROUTINES
Page0-to-ProgramJumps
PAGE0, PAGE1
These terms do not involve '508A programming however, since we are using a PIC'84 chip in the Pseudo'508A module, Page0 and page1 instructions are needed in the "SetUp" routine.
The program in the PIC'84 is situated at page0. This is also called Bank0. The TRIS registers (TRISA and TRISB) are located in Bank1 (Page1) and to get to page1, bit5 in the Status register (address 03h) must be SET.
The instruction is: BSF 03,5
When the micro is turned on, it comes on with Page0 being the page you can
access. To access Page1, the instruction BSF Status,5 takes the program to Page1.
There are three ways to move (load) a value into the TRISB register:
MOVLW xx
MOVWF TRISB
BCF TRISB,0 ;Make GP0 output
BCF TRISB,1 ;Make GP1 output
BSF TRISB,2 ;Make GP2 input
MOVLW xx
MOVWF 86h
After the TRISB register has been loaded with the value to make the required port-lines input or output, the program must be taken back to Page0 (bank0) so the program can be placed at page0. The instruction is: BCF 03,5
See Set-Up for instructions.
PAUSE
- See also Time Delay for 0.1 sec delay and 0.25 second delay
Pause is the same as DELAY. It is a 1 millisecond delay, designed to operate with a 3.579545MHz colour-burst crystal.
If you have an RC oscillator at about half this frequency, the Pause routine will take 2 milliseconds to execute.
To call Pause, use the instruction:
CALL Pause
After Main, type the following sub-routine:
Pause MOVLW EB
;Put 235 cycles in W
MOVWF 1C
Loop1 MOVLW 0B
;Put 11 cycles in W
MOVWF 1D
Loop2 DECFSZ 1D,1
GOTO Loop2
DECFSZ 1C,1
GOTO Loop1
RETURN
If you want Pause for 2 milliseconds type:
CALL Pause
CALL Pause
Pause_mS
If you want to pause for more than a few milliseconds, Call Pause_mS. It will produce a delay from 1 millisecond to 9,999 milliseconds.
Before calling Pause_mS, place the value of the delay you require in files 1A and 1B.
Files 1A and 1B are set up for 00 01 to 99 99 milli-seconds, where 1A is the Higher and 1B is the lower value.
E.g: For a delay of 2 milliseconds, load the value 00 02 into 1A and 1B via W then call Pause_mS:
MOVLW 00
MOVWF 1A
MOVLW 02
MOVWF 1B
CALL Pause_mS
The values in 1A and 1B must be in hex. Use the following table to find the hex values:
05 = 05
55 = 37h
10 = 10
60 = 3C
15 = 06
65 = 41h
20 = 14h
70 = 46h
25 = 19h
75 = 4B
30 = 1E
80 = 50h
35 = 23h
85 = 55h
40 = 28h
90 = 5A
45 = 2D
95 = 5F
50 = 32h
00 for 1A = 00
00 for 1B = 01
Examples:
300 milliseconds = 03 00
625 milliseconds = 06 25
1,100 milliseconds = 01 10
5 seconds = 50 00
10 seconds = 99 99
Place the Pause_mS sub-routine after Main:
Pause_mS
MOVF 1B,0
;Move 1B to W
MOVWF 19h
;Move W to 19h
Loop1 MOVLW F8
;Put 248 cycles in W
MOVWF 1C
;Put 248 into 1C
Loop2 MOVLW 0B
;Put 11 cycles in W
MOVWF 1D
;Put 11 into 1D
Loop3 DECFSZ 1D,1
GOTO Loop3
DECFSZ 1C,1
GOTO Loop2
DECFSZ 19h,1
GOTO Loop1
INCF 1A,1
DECFSZ 1A,1
GOTO Loop4
RETURN
;Return to Main etc
Loop4 MOVLW 64h
;Put 100 loops into W
MOVWF 1B
;Load 1B with 100
Loop5 MOVLW F8
;Put 248 cycles in W
MOVWF 1C
;Put 248 into 1C
Loop6 MOVLW 0B
;Put 11 cycles in W
MOVWF 1D
;Put 11 into 1D
Loop7 DECFSZ 1D,1
GOTO Loop7
DECFSZ 1C,1
GOTO Loop6
DECFSZ 1B,1
GOTO Loop5
DECFSZ 1A,1
GOTO Loop4
RETURN
;Return to Main etc
Pause_mS uses the 1 millisecond routine and executes it "X" number of times. If the value is 315mS, for example, it executes the routine 15 times then looks at the high value (03).
If the value is zero, it detects the zero by incrementing 1A then using the instruction DECFSZ. The result will be zero and the sub-routine will return to the Main program.
If the high value is 1 or greater, the 1mS routine will be called 100 times (64h times), for each unit in the high file, then return to Main.
The secret to creating a delay routine is to nest the files and load the very inner file with a fairly low value. This way you can increment or decrement the next inner file by a value of one and it will have
the smallest effect on the overall delay time. This is how you fine-tune the delay to the exact time.
Basically, to work out the timing for the delay, the micro divides the clock by 4 and the result is a length of time called a Machine Cycle or Instruction Cycle. Each instruction takes 1 Instruction-cycle
except for any program branches such as GOTO. Add up the Machine cycles for the nested delay and you have the total time for execution of the routine.
For the 1mS delay the timing is worked out via the following formula:
1C(1B x 1A x 3 + 1B x 5) + 1C x 5
PC BOARDS
When making a PC board, the unused pins of the port(s) should not be connected to ground or positive but left OPEN. It is best to take each one to a solder land and connect another solder land (having
a hole) to the pad so that a component such as a test LED can be connected at some later date.
Leave the port line OPEN and configure the line as an OUTPUT. Write a zero (LOW) to the line and it will consume the least power.
PIC12C508A
All the programs and information in this chapter refers to a PIC12C508A microcontroller. See Converting '508A programs to PIC'84.
PIC16F84
- See converting '508A programs to PIC'84.
The PSEUDO'508A uses a PIC16F84 microcontroller to mimic a '508A microcontroller.
Programs written for a '508A can run directly in a PIC'84. The reason we do this is because the '84 can be re-programmed, while the '508A is a One Time Programmable chip.
The only instruction to be changed for a PIC'84 or Pseudo'508A is the accessing of the in/out register (TRIS in the real '508A).
The instruction:
TRIS 06
must be replaced with:
BSF 03h,5
;Select Page1
MOVLW 00
MOVWF 06,1
BCF 03h,5
;Select Page0
The value to be placed in W depends on the arrangement you require for the input and output lines.
In the '84, the in/out ports (PortA and PortB) are at page0. The control registers for these ports (the TRISA and TRISB registers) are at page1(also called bank1). You have to get to page1 (bank1) via the instruction BSF 03h,5 and load the TRISB file (register) with the appropriate value. When in page1 (bank1) the TRISB register has the address value 06. This is shown in the routine above as MOVWF 06,1. The routine then selects page0 via the instruction BCF 03h,5.
With the '508A you can go directly to the TRIS file.
PIEZO
A Piezo is a device that produces a loud sharp tone when a voltage is placed across it then removed. It takes very little current to drive the device and can be driven directly from any of the outputs of the '508A.
POLLING
Reading an input within a loop (such as a Main routine).
POT
POT is routine to measure a potentiometer, photocell, thermistor or any variable resistance in the range 0k to approx 50k.
The device must be connected as shown in the diagram. As the variable resistor changes resistance, the mark-space ratio from GP1 changes and this causes the LED to alter in brightness. If a motor is connected to GP1 via a buffer transistor it will increase in speed as the pot is rotated.
POT routine has to be set up the first time the chip is turned on.
To set up POT, turn the potentiometer to FULL resistance and supply power to the chip. The LED will flash for 0.5 sec. Turn the pot to minimum resistance. The LED will flash again and immediately take
a reading.
The set-up is complete. Turn the pot and the LED will alter in illumination.
This routine can be used to vary the speed of a motor or the brightness of a lamp. Simply put a buffer transistor on output pin GP1, via a buffer resistor, and the motor can be controlled or the lamp varied
in brightness.
The set-up routine for POT must be placed in the set-up section. This is at address 000.
Set_Up CALL PotSetup
GOTO Main
Before Main, place the PotSetup sub-routine:
PotSetup
CALL HiVal
;Disregard 1st result
CALL HitVal
MOVF 1F,1
;Move 1F to W. Move
MOVWF 18h
; "HighVal" count to 18h
MOVLW 00
;Load W with 000 0000
TRIS 06
;Make GP1 output
BSF 06,1 ;Make GP1 HIGH
MOVLW 08
;Put 8 into 1C for 1 sec
MOVWF 1C
; turn-on for LED
CALL Delay
;1 sec delay
BCF 06,1
;Make GP1 LOW
MOVLW 20
;Put 20 into 1C for 4 sec
MOVWF 1C
; turn-on for LED
CALL Delay
;4 sec delay
BSF 06,1
;Make GP1 HIGH
MOVLW 08
;Put 8 into 1C for 1 sec
MOVWF 1C
; turn-on for LED
CALL Delay
;1 sec delay
CALL LoVal
;Disregard 1st result
CALL LoVal
MOVF 1F,0
;Move 1F to W.
MOVWF 19h
; "LowVal"" to 19h
RETURN
Hi_Val MOVLW FF
MOVWF 1B
;1B is delay value
HV1 CLRF 1F
;Carries Pot value to file
MOVF 1B,0
; create value for 1F via 1B
MOVWF 1C
; 1F must be 250+
MOVLW 00
;Load W with 00
TRIS 06
;Make all output
BSF 06,2
;Make GP2 HIGH
MOVLW FF
;Delay to charge cap
MOVWF 1A
HV2 DECFSZ 1A,1
GOTO HV3
BCF 06,2
;Make GP2 LOW
HV3 MOVLW 04
;Load W with 000 0100
TRIS 06
;Make GP2 input
ANDWF 06,0
;AND W with input port
BTFSC 03,2 ;Test Z flag in STATUS
GOTO HV5
;Input LOW, end counting!
INCF 1F,1
;Input HIGH, Inc count file
HV4 DECFSZ 1C,1
GOTO HV4
GOTO HV3
HV5 MOVLW 05
;See if 1F is 5 off 256!
MOVWF 1D
MOVLW FF
;Compare 1F with W
HV6 XORWF 1F,0
BTFSC 03,2
RETURN
;1F will come out 250!
INCF 1F,1
DECFSZ 1D,1
GOTO HV6
DECF 1B,1
GOTO HV1
LoVal MOVF 1B,0
; create value for 1F via 1B
MOVWF 1C ;
CLRF 1F
;Carries Pot value to file
MOVLW 00
;Load W with 00
TRIS 06
;Make all output
BSF 06,2
;Make GP2 HIGH
MOVLW FF
;Delay to charge cap
MOVWF 1A
LV1 DECFSZ 1A,1
GOTO LV1
BCF 06,2
;Make GP2 LOW
LV2 MOVLW 04
;Load W with 000 0100
TRIS 06
;Make GP2 input
BTFSS 06,2
;Test GP2
RETURN
;Input LOW, end counting!
INCF 1F,1
;Input HIGH, Inc count file
PV3 DECFSZ 1C,1
GOTO LV3
GOTO LV2
HighVal will be placed in file 18h and LowVal will be in file 19h.
In the Main program, call Pot:
CALL Pot
Before Main, include the Pot sub-routine:
Pot
PROGRAM LAYOUT
Programs should be laid out as follows:
StartUp ---------
---------
---------
GOTO Main
Table1 ADDWF 02, 1
RETLW data
RETLW data
;up to FE Maximum
Sub-routine1:
GetKey ---------
---------
---------
RETURN
Sub-routine2:
Convert1 ---------
---------
---------
RETURN
Sub-routine3:
Display1 ---------
---------
---------
RETURN
Main ---------
---------
CALL GetKey
CALL Table1
CALL Convert1
---------
GOTO Main
PROGRAM JUMPS
See Calculated Program Jumps.
|
