SP2-433-160 Datasheet, PDF (25/27 Pages) Radiometrix Ltd – UHF SpacePort Transceiver

**********************************************************************
* SUBROUTINE: OUT_BYTE
**********************************************************************
*This subroutine will output of one byte to the SP2. Register X
*should contain the address of the memory location of the byte to be *send.
*Note: that register X has to be pre-loaded before entering this *
subroutine.
OUT_BYTE
WAIT_ACC
WAIT_REQ
WAIT_TXA1
WAIT_TXR1
LDAA
ANDA
LDAB
ANDB
STAB
LDAB
BITB
BNE
LDAB
STAB
ORAA
STAA
LDAB
ORAB
STAB
LDAB
BITB
BEQ
LDAA
LSRA
LSRA
LSRA
LSRA
LDAB
ANDB
STAB
LDAB
BITB
BNE
ORAA
STAA
LDAB
ORAB
STAB
LDAB
BITB
BEQ
RTS
0,X
#%00001111
PORTC
#%11101111
PORTC
PORTC
#%00100000
WAIT_ACC
#%10011111
DDRC
#%10000000
PORTC
PORTC
#%00010000
PORTC
PORTC
#%00100000
WAIT_REQ
0,X
PORTC
#%11101111
PORTC
PORTC
#%00100000
WAIT_TXA1
#%10000000
PORTC
PORTC
#%00010000
PORTC
PORTC
#%00100000
WAIT_TXR1
;GET THE BYTE TO SEND TO SP2
;PREPARE LEAST SIGNIFICANT NIBBLE
;FORCE TX-REQUEST LOW
;WAIT FOR TX ACCEPT TO GO LOW
;CHANGE DATA DDRC TO OUTPUT
;TURN BUS DRIVE ON
;MAKE SURE RXA IS HIGH
;OUTPUT DATA
;FORCE TX-REQUEST HIGH
;WAIT FOR TX_ACCEPT TO GO HIGH
;PREPARE MOST SIGNIFICANT NIBBLE
;BY SWAPPING THE LS- & MS-NIBBLE
;FORCE TX-REQUEST LOW
;WAIT FOR TX-ACCEPT TO GO LOW
;OUTPUT DATA
;FORCE TX-REQUEST HIGH
;WAIT FOR TX_ACCEPT TO GO HIGH
**********************************************************************
* SUBROUTINE: LISTEN TO BUS
*********************************************************************
*
*This will turn the SP2 host to listen mode again and should
*be called when the whole packet has been sent to the SP2
*
LISTEN_BUS LDAA #%10010000 ;PUT PORT BACK TO LISTEN
STAA DDRC
RTS
*********************************************************************
Radiometrix Ltd, SP2 data sheet
page 25