Question

Can anyone explain this code? I get the gist of it, but having someone explain this code would be helpful

;*****************************************************************
;   Data section   
;*****************************************************************
   ORG DATA  

;*****************************************************************
;    Main program section   
;*****************************************************************
   ORG CODE  
Main:
LDS #STACK
LDAA #%00000100
STAA DDRT
  
LDAA #$80
STAA TSCR1
LDAA #$07
STAA TSCR2
BSET TIOS, %00000100
LDAA #$10
STAA TCTL2
CLI
LDAA #$04
STAA TIE
  
  
Here
NOP
BRA Here

;*****************************************************************
;    Subroutine section
;*****************************************************************
;*****************************************************************
;    Interrupt ISR
;*****************************************************************

TC2_ISR

LDD TCNT
ADDD #30000
STD TC2
BSET TFLG1,%0000100
RTI
  

;*****************************************************************
;    Interrupt Vectors
;*****************************************************************
ORG $FFDE
DC.W TC2_ISR
  
   ORG $FFFE
   DC.W Main   ;Reset Vector

Answer 1

• PT2 used as a output.
• Timer channel 2 is used to generate ISR

;*****************************************************************
; Data section   
;*****************************************************************
ORG DATA

;*****************************************************************
; Main program section   
;*****************************************************************
ORG CODE
Main:
LDS #STACK   //initialize stack pointer
LDAA #%00000100 //put 00000100 into A
STAA DDRT //to make PT2 as output and other pin as input
  
LDAA #$80 //put $80 into A,if you use $90, then NO need for "BSET   TFLG1, %00000100" in ISR Routine
STAA TSCR1 //enable timer
LDAA #$07 //put $07 into A
STAA TSCR2 //set Prescaler=128
BSET TIOS, %00000100 //set Channel 2 as output channel,toggle PT2 Pin
LDAA #$10 //put %00010000 into A
STAA TCTL2 //store %00010000 to TCTL2 so that OM2=0,and OL2=1,make PT2 pin toggle everytime when there is a match between TC2 and TCNT
CLI //Enable IRQ
LDAA #$04 //put $04 into A
STAA TIE //CH2 interrupt Enable
  
  
Here
NOP
BRA Here //Keeps looping to "Here" Forever

;*****************************************************************
; Subroutine section
;*****************************************************************
;*****************************************************************
; Interrupt ISR
;*****************************************************************

TC2_ISR //Timer Channel 2 (TC2) interrupt vector

LDD TCNT //Load D with TCNT(load current timer count to D)
ADDD #30000 //stores to TCTL3 (Toggle D once every 30000 timer pulses)
STD TC2 //Store D to TC2
BSET TFLG1,%0000100 //Clear the Channel 2 Timer flag for next round (writing HIGH will clear it)
RTI //return from interrupt
  

;*****************************************************************
; Interrupt Vectors
;*****************************************************************
ORG $FFDE
DC.W TC2_ISR
  
ORG $FFFE
DC.W Main //Reset Vector.CPU wakes here and it is sent to start of the code at stack Pointer which is initialize in main