A circuit with PIC18F4550 microcontroller is interfaced to a DAC0808 and an Op-Amp as shown in the figure above.

A program written in assembly language targeted for the circuit above is listed as below:

ORG 0000H

CNT1 EQU 0x30 ; 0x30 is the location for CNT1

CLRF TRISB, 1 ; Set to output

MOVLW 0x01

MOVWF PORTB

LOOP1: MOVLW 0b11001

MOVWF CNT1 ; Put this binary no. into CNT1

LOOP2: RLNCF PORTB, 1, 0 ; Rotate Left

DECF CNT1, 1, 0 ; Decrement CNT1

BNZ LOOP2 ; Jump to LOOP2 if not zero

BRA LOOP1 ; Jump to LOOP1

END: ; End of program

The crystal frequency is 16MHz and each instruction takes 4 cycles to execute.

The output voltage range of the DAC is set to between 0-5V.

Based on the circuit, program and the given conditions,

(a) Sketch and label the output waveform of this circuit for 2 cycles. Show the necessary calculations.

(b) Rewrite the given program in C language. Show only the main function. Use the library function Delay10TCY(x) to generate the desired delay.

IREF 2mA RREF 2.5k 3 14 DO D1 D2 D3 DAC0808 D4 D5 D6 D7 VREF +5V RB0 RB1 U RB2 15 5k 2.5k 00 RB4 URB6 0 12 6 OP AMP 0 OUTPUT 3 VEE-15V