Subject:
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Re: Extra output for clocking (Using Hardware Output Compare)
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 7 Dec 1998 12:57:23 GMT
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Original-From:
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fthompson9@aolNOMORESPAM.com
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Viewed:
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1251 times
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Hugo:
I am not going to be able to answer this one fully. We will need to hear
from others on the list to hear how to mix assembler code into an IC program,
how to have the IC program modify assembler variables, and how to set up
interrupt service routines.
The following code fragments are from the Toshiba TMP68HC11 Reference
Manual 1990. I have only added extra comments to make this more specific to
your application. I hope this helps and I hope others can supply the missing
pieces. If so, you may generate clock pulses over 100KHz.
The assembler presented in the manual is broken into two parts. First there
is a "set up" procedure that initializes control registers and set the
interrupt vector. This could probably be done in IC. The Interrupt Service
Routine (ISR) should be written in assembler. The hardware is expectin the
STD command to load new values into the output compare function and using a
different type of store could result in premature triggering of the output.
Numbers proceeded with a $ are hexidecimal, numbers preceeded with a numbers
preceeded with a % are binary, # are litterals (don't fetch from address).
Setup:
write the command "Jump To my ISR (SV50C2)" into the memory at the interrupt
vector
for output compare 2
LDA #$7E ;Extended Jump Op Code
STAA P0VOC2 ;(This is defined as $00DC on the Evaluation Board)
LDX #SV50C2 ;Address of my interrupt service routine
STX PVOC2+1 ;Finish JMP instruction to my timer routine
now set up control register so that the output pin will toggle state each time
the Output Compare Register matches the free running timer value and generates
an interrupt. The value loaded will need to be changed for each OC register
used. Use the logical Or of the following values to set up the desired OC
registers. Some care must be observed in this part to preserve what the rest
of IC and the Handy Board is doing. Someone please address the issue of how
the LCD control TOC4 is to be set up.
0100 0000 OC2
0001 0000 OC3
0000 0100 OC4
0000 0001 OC5
LDX #REGBAS ;Point to register block ($1000 on the Evaluation Board)
LDAA #%01000000 ;OM2:OL2 = 0:1 (toggle state of TOC2 each interrupt)
STAA TCTL1,C ;Setup OC2 to toggle on compare
LDAA #%01000000 ;For OC2 it is the same value but for others:
0100 0000 OC2
0010 0000 OC3
0001 0000 OC4
0000 1000 OC5
STAA TFLG1,X ;Clear any pending OC2F flag
STAA TMSK1,X ;Enable OC2 interrupts
CLI ;Enable all unmasked hardare interrupts
TMSK1 = $22
TFLG1 = $23
That is all we need to do for setup. The interrupt service routine contains
the number that controlls the speed of the output signal. In this examble it
is called HDLY. This is the variable that should be consistant with your IC
program. You should write a program that varies this number to ramp up and
down the speed of your stepper. If it is easy you just include the variable
in your ramping code. If it is hard, you write a subroutine that modifies
this value. Remember that as the number gets larger the clock signal gets
slow. Also remember that changes in small timer values make great changes in
frequency. (This problem has given me trouble many times in the past.) If
your decrease your timer dealy by two when the timer value is $07FF to $07FD,
your frequency changes less than one percent. If you change the delay value
from 4 to 2 the frequency doubles.
I should also mention that the Interrupt service routine seems to assume
that the X register is pointing the the register block. Above we seemed to
need to set this explicitly. This is another item the IC experts will need to
comment on. Now here is the interrupt service routine:
SV5OC2:
LDD HDLY ;Get Delay time for 1/2 cycle (Your variable here)
ADD TOC2,X ;Add to the last compare register value
STD TOC2,X ;Update OC2 [Schedule next edge] (The value MUST be stored with
this instruction)
BCLR TFLG1,X $BF ;clear OC2F
RTI ;thats it, the pin will chage again after this delay
other values for the bit clear function:
$BF OC2
$DF OC3
$EF OC4
$F7 OC5
TOC1 = $16
TOC2 = $18
TOC3 = $1A
TOC4 = $1C
TOC5 = $1E
Well for what it's worth. That is how you use the hardware timer
function. They require software service to make them more versatile. If you
get this implimented, your motors should really hum. If not,... well have you
considered DC?
Hope this helps,
Pherd
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