120 lines
5.0 KiB
TeX
120 lines
5.0 KiB
TeX
\documentclass[11pt]{article}
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\author{Jonathan Chan (15354146)}
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\title{PHYS 319\\Labs 1 and 2 Notes}
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\usepackage{listings}
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\usepackage{alltt}
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\usepackage{fullpage}
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\begin{document}
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\maketitle
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\section{Lab 1}
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\section{Lab 2}
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Some minor reminders:
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\begin{itemize}
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\item Remember to connect +5V and ground to 4-digit 7-segment display, and ground (\textbf{not} VCC) to microprocessor
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\item \texttt{mspdebug} needs to be exited (with CTRL-D) for the program to run
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\end{itemize}
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\subsection{Student Number}
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There needs to be a move to \texttt{P1OUT} for setting each digit. Since the strobe also needs to go from low to high to actually set the digit, there are actually two moves for each digit. Below is the full program for setting the display to \texttt{4146}.
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\begin{alltt}
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.include "msp430g2553.inc"
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org 0xc000
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START:
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; setup
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mov #0x0400, SP
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mov.w #WDTPW|WDTHOLD, \&WDTCTL
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mov.b #11110111b, \&P1DIR
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; set digits
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mov.b #01100000b, \&P1OUT ; xxx6
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mov.b #01100001b, \&P1OUT ; xxx6
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mov.b #01000010b, \&P1OUT ; xx46
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mov.b #01000011b, \&P1OUT ; xx46
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mov.b #00010100b, \&P1OUT ; x146
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mov.b #00010101b, \&P1OUT ; x146
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mov.b #01000110b, \&P1OUT ; 4146
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mov.b #01000111b, \&P1OUT ; 4146
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; disable
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bis.w #CPUOFF, SR
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org 0xfffe
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dw START
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\end{alltt}
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\subsection{Program 1}
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Below is the full program annotated with comments. Making the lights blink twice as fast is simply halving the initial value set in R9, but making them blink twice as slow involves decrementing another register, since the doubled value is 80000 and will not fit in a two-byte word whose maximum value is 65536.
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\begin{alltt}
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.include "msp430g2553.inc"
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org 0xC000
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START:
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mov.w #WDTPW|WDTHOLD, \&WDTCTL
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mov.b #0x41, \&P1DIR ; #01000001b (P1.6 == LED2, P1.0 == LED1)
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mov.w #0x01, R8 ; #00000001b (start on LED1)
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REPEAT:
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mov.b R8, \&P1OUT
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xor.b #0x41, R8 ; #00000001b -> #01000000b -> ... (LED0 -> LED1 -> ...)
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mov.w #40000, R9 ; counts to decrement before blink
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mov.w #40000, R10 ; counts to decrement (2nd dec, since max val is 65536)
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WAITER1:
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dec R9
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jnz WAITER1 ; R9 not yet 0
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WAITER2:
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dec R10
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jnz waiter2 ; R10 not yet 0
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jmp repeat ; R9, R10 == 0; blink other LED
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org 0xfffe
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dw START ; set reset vector to 'init' label
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\end{alltt}
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\subsection{Program 2}
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To make the LEDs cycle in the order
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\\ \indent \texttt{none -> red -> green -> both -> none},\\
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the output to P1OUT needs to be
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\\ \indent \texttt{0000 0000 -> 0000 0001 -> 0100 0000 -> 0100 0001 -> 0000 0000}.\\
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Notice that
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\\ \indent \texttt{0000 0000 -> 0000 0001} \indent and \indent \texttt{0100 0000 -> 0100 0001}\\
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can be done with an \texttt{xor} on \texttt{0000 0001}, and
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\\ \indent \texttt{0000 0001 -> 0100 0000} \indent and \indent \texttt{0100 0001 -> 0000 0000}\\
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can be done with an \texttt{xor} on \texttt{0100 0001}. Rather than using two registers to save the two different values to \texttt{xor} on, notice that in turn
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\\ \indent \texttt{0000 0001 -> 0100 0001 -> 0000 0001}\\
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can be done with an \texttt{xor} on \texttt{0100 0000}. Then we initialize a register (\texttt{R8} here) to \texttt{0000 0001}, and after we have \texttt{xor}ed it with the output, we \texttt{xor 0100 0000} on \texttt{R8} to get the next value that should be \texttt{xor}ed with the output. Below is the full program annotated with comments.
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\begin{alltt}
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#include "msp430g2553.inc"
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org 0x0C000
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RESET:
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mov.w #0x400, SP
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mov.w #WDTPW|WDTHOLD, \&WDTCTL
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mov.b #11110111b, \&P1DIR ; all pins outputs except P1.3
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mov.b #00001000b, \&P1REN ; enable resistor for P1.3
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mov.b #00001000b, \&P1IE ; P1.3 set as an interrupt
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mov.w #0x0049, R7 ; R7 = 0000 0000 0100 1001
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mov.b R7, \&P1OUT ; LED1, LED2 on
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mov.b #0x0041, R8 ; value to xor with R7
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EINT ; enable interrupts
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bis.w #CPUOFF, SR
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PUSH:
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xor.w R8, R7 ; next LED state
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xor.w #0x0040, R8 ; 0x0041 -> 0x0001 -> 0x0041
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mov.b R7, \&P1OUT ; set LEDs to new state
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bic.b #00001000b, \&P1IFG ; interrupt flag P1.3 set to 0
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reti ; return from interrupt
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org 0xffe4
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dw PUSH ; interrupt from button goes here
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org 0xfffe
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dw RESET ; interrupt from reset button goes here
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\end{alltt}
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\end{document} |