CPU 8052

          INCLUDE stddef51.inc

CLOCK    equ 115200*16
defbaud  equ 115200

powers   EQU 20h

         jmp overvec

t0start:
          REPT 0bh-t0start
          nop
          ENDM
         reti


;=================================

overvec:

         mov  sp, #12
         mov  p1, #00000111b
         mov  p3, #11111111b

         mov  ie, #0
;        mov  ien1, #0
         mov  tcon, #01000000b
         mov  tmod, #00100011b
         mov  scon, #01110000b              ;mode 1
         mov  th1,  #256-CLOCK/16/defbaud   ;rs232 baud
         orl  pcon, #10000000b              ;rs232 clock /16

         mov  powers, #00011100b
mainloop:
rxwait:
         jnb  ri, rxwait                         ;wait for rs232 byte received

         clr  ri
         mov  a, sbuf                            ;bit0=reply, bit1=powerswitch
         mov  b, a

         jnb  acc.1, nopower

         mov  powers, a
         jmp  mainloop
nopower:
         anl  a, #11111000b
         mov  c, powers.2
         mov  p3.7, c                            ;Vpp=0v
         mov  c, powers.3
         mov  acc.1, c                           ;Vpp=12v
         mov  c, powers.4
         mov  acc.2, c                           ;Vcc=5v
         mov  p1, a 

         jnb  b.0, mainloop                      ;no reply

         mov  a, p1
         mov  sbuf, a                            ;send p1 

         jmp mainloop        

         END