AN1833 Freescale Semiconductor / Motorola, AN1833 Datasheet - Page 38

• Manufacturer Part Number: AN1833
• Description: A Low-Power Wireless Remote Control Transmitter and Receiver
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
BAUD_SEL
*** RAM variable allocation:
char
count
cmpr
xcnt
length
buffer
flag
************************************************************************************
*
*
*
main
Wait_for_data brset
look_again
************************************************************************************
* frontporch -takes a 4-bit sample and looks for logic 1
************************************************************************************
front_porch
38
org
rmb
rmb
rmb
rmb
rmb
rmb
rmb
org
rsp
ldx
jsr
lda
sta
inc
bcc
lda
sta
bra
equ
jsr
rora
rorx
rora
ror
lda
jsr
tsta
dec
bne
lda
cmp
beq
jmp
equ
1
1
1
1
1
8
1
0C0
*******************************
* beginning of EPROM space
*******************************
300
#$0
init
#$4
count
rxd,PORTB,front_porch ; branch if incoming data =1
xcnt
Wait_for_data
#$00
xcnt
Wait_for_data
*
get_bit
char
#2*(BAUD_SEL-3)
delay_13a
count
front_porch
#$f0
char
get_data
main
Freescale Semiconductor, Inc.
$08
For More Information On This Product,
Go to: www.freescale.com
; BAUD_SEL
; $04 19.2 k 9600
; $08
; $10 4800
; $20 2400
; $40 1200
; $80
; start at the top of ROM
; reset the stack pointer
; clear flags
; initialize port pins & ints
; load bit counter to 3
; increment a count
; check for incoming data
; carry set so clear the count
; and go back to examining data
;[39] sample data bit
;[3] noise bit -> carry
;[3] carry -> noise data reg
;[3] filtered data bit -> carry
;[5] carry -> char
;[2] prepare for 1 bit delay
;[13a+12] execute delay routine
;[3] for timing purposes only
;[5] bit received, dec count
;[3] loop if more bits to get
; check for bit value received
; looking for 4 one bits
; four logic 1 bits received - go wait
; for incoming data
; invalid frontporch -restart
; incoming data register
; temp storage variable
; compare register
; counter
; index pointer storage
; receiver buffer
; flag bits
600
*
4MHz osc
9600
2400
1200
600
300
- bit 0 = got a 55
4800
2MHz osc
MOTOROLA
AN1833
*