Subject:
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D/A converter
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 11 Jun 1998 05:56:54 GMT
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Original-From:
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HECTOR NORIEGA <110060.2126@compuserve.AVOIDSPAMcom>
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Viewed:
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1186 times
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"Hi", from Hector Noriega, I am trying to send a data byte from port C out
to a D/A converter
faster than 1KHZ (target about 10KHZ) . I wrote a test subroutine in
assembly code but I can
not enable the address decoder using port B for the msb and port C for the
lsb and the data.
The command that works in "IC" is poke(6fff, data).
Could someone give me a hint with the assembly code?
****************Here is the assembly code*************************
* PIOT.ASM Port I/O test; Program by Hector Noriega, 07JUNE98
* this program is to send data to an external Digital to Analog conv..
* the main purpose is to characterize how fast can a byte output
* be latched into the D/A converter.
* using port "B" with a msb address of $6F to enable HB decoder U6 to
* enable (y4) on the expansion bus j3-5. Port C outputs the data
* byte for the D/A.
* Using IC the command to accomplish the same thing is
* poke(0x6fff,volt_out); /* D/A */
#include "6811regs.asm"
ORG MAIN_START
subroutine_od2a:
LDX #BASE
LDAA #$60
STAA HPRIO,X ; test SMOD & MDA bit(normal expanded mode)
LDAA #$00
STAA PIOC,X
SEI ; turn off system interrupts so that
LDAA #$FF ;
STAA DDRC,X ; Set portc to output
STAA PORTC,X ; store in latch low byte address
LDAA #$6F ; 6F load with msb address
LDAB #128 ; data = 0 for bypolar Digital to Analog
Converter
STAA PORTB,X ; msb byte address
STAB PORTC,X ; low byte is data
CLI ; turn on interrupts*/
RTS
*************************** Here is the C program ****************
* Feedback Controller */
int v_opt;
void main()
{
while(1)
{
v_opt = od2a(0);
} /* end of while */
} /* end of main program*/
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