Code Examples from Class
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- Factorial
; Factorial Calculation ; The answer is in R10 ; Rob Frohne 2013 GLOBAL Reset_Handler AREA Factorial, CODE, READONLY ENTRY Reset_Handler movs r8, #0 ; Take the factorial of this number, n. mov r10, #1 ; 0! and 1! are 1 beq stop ; If r8 is zero we are done cmp r8, #1 ; If r8 is 1, beq stop ; we are done subs r9, r8, #1 ; n-1 loop mulne r10, r9, r8 ; n(n-1) mov r8, r10 subs r9, r9, #1 bne loop stop b stop END
- 64 Bit Add
VAL1A EQU 0xffffffff VAL1B EQU 0x0000000f VAL2A EQU 0x00000001 VAL2B EQU 0x00000001 AREA LongAdd, CODE ENTRY ldr R0, = VAL1A ldr R1, = VAL1B ldr R2, = VAL2A ldr R3, = VAL2B adds R8,R0,R1 adcs R9,R1,R3 stop b stop END
- Copy to RAM
AREA Exaddress, CODE, READONLY EXPORT Reset_Handler Reset_Handler LDR R9, =list mov R7, #4 ; number in list ldr r6, =datastart loop ldr r8,[r9],#4 str r8,[r6],#4 subs r7,r7,#1 bne loop stop b stop ALIGN list DCW 0x1111, 0x2222, 0x3333, 0x4444, 0x5555 ALIGN string DCB "This is a test.",0 ; This string is not used in the copy to ram program string2 DCB 'T','h','i' ; This string2 is not used in the copy to ram program ALIGN AREA Thedata, DATA, NOINIT, READWRITE datastart SPACE 20 END
- Subroutine Example1
; First Subroutine Example
; This program demonstrates using a subroutine,
; saving registers on the stack, etc.
; Rob Frohne, 1/3/2013
stack_start EQU 0x40001000
AREA Subroutine_Example, CODE
ENTRY
Start
ldr sp, =stack_start ; Tell where we will place the stack.
; (It goes down (lower addresses from here.)
mov r1, #1 ; Store some numebers in some registers
mov r2, #2
mov r3, #3
bl subroutine
stop b stop
; This subroutine saves the registers,
; messes up the registers locally,
; then restores the registers and returns.
subroutine
stmfd sp!, {r1-r2,lr} ; save used registers and the link register (r14)
mov r1,#0xffffffff ; mess up the registers
mov r2, r1
ldmfd sp!, {r1,r2,pc} ; pop the stack and return
END
- Minimum of a Signed Number
; This program finds the minimum of a list of constant words in signed format ; The result is in r3 at the end of the routine. ; Rob Frohne 10/30/2013 AREA Program, CODE, READONLY ENTRY ldr r0,=end ; load the beginning address of the code & initialize it as the pointer. ldr r2,=begin ; load the ending address of the code. mov r3,#0x7fffffff ; Initialize r3 as the most positive number. loop ldr r6,[r2],#4 ; load the next data into r6 and post increment r2 for the next data. cmp r6,r3 ; Find out if r6 > r3. result from r6-r3 like subs r7,r6,r3 without r6 necessary. bgt no_update ; If it is no update. mov r3,r6 ; update if r6 is lower than r3. no_update cmp r0,r2 ; are we at the end yet bne loop ; if r7 != 0 then keep looping stop b stop ALIGN begin DCD 0x8fffffff, 0x55555555, 0x44444444, 0x77777777, 0xffffffff end END
- Compare Two Null Terminated Strings
; Subroutine to compare two null terminated ASCII strings.
; The address where the two strings start are in r0 and r1
; The return is in r0, 1 for match and 0 for don't match.
; If they don't match, r1 gives the number of the first
; character that didn't match, starting with 0.
; r2 and r3 are not protected.
; Rob Frohne 11/6/2013
stack_start EQU 0x40001000
AREA String_Compare, CODE
ENTRY
Start
ldr sp, =stack_start ; Tell where we will place the stack.
; (It goes down (lower addresses from here.)
ldr r0, =string1
ldr r1, =string2
bl compare_strings
stop b stop
compare_strings
stmfd sp!, {r2,r4,r5,lr} ; save used registers and the link register (r14)
mov r2, #0 ; Initialize the counter for the first position.
loop
ldrb r4,[r0],#1
ldrb r5,[r1],#1
cmp r5,r4
bne do_not_match
cmp r4, #0 ; check for end of string.
beq match
add r2, #1
b loop
do_not_match
mov r0, #0 ; don't match
b finish
match
mov r0, #1
finish
mov r1,r2 ; Move the count into the result register.
ldmfd sp!, {r2,r4,r5,pc} ; pop the stack and return
string1
DCB "This is the first string.",00 ; For testing purposes.
ALIGN
string2
DCB "This is the first string.",00
ALIGN
END
- BCD Add
; Subroutine to add two BCD numbers in 32 bit form with each nibble
; representing a digit.
; locals: r8 for digit counter, mask 0xf, r5 & r6 for masked addends,
; working BCD_carry, r7 for
; working result in r4
; the summed digits go in r3
; inputs: r0+r1
; outupts: r0 result and r1 carry
; only r4-r8 are saved.
; Rob Frohne 11/12/13
stack_start EQU 0x40001000
AREA ADD_BCD, CODE
ENTRY
Start
ldr sp, =stack_start ; Tell where we will place the stack.
; (It goes down (lower addresses from here.)
ldr r0, =0x12345678 ; The two numbers to add.
ldr r1, =0x87654321
bl bcd_add
stop b stop
bcd_add ; The subroutine
stmfd sp!, {r4-r8,lr}
mov r8, #8 ; Set the counter to move through the eight digits
mov r7, #0 ; Set the carry to zero to start with
mov r3, #0 ; This is where the resulting digits of the sum are stored.
loop
and r5, r0, #0xf ; mask for the rightmost digit.
and r6, r1, #0xf
add r4, r5, r7 ; add carry
add r4, r4, r6 ; r4=r5+r6
subs r4, r4, #10 ; Subtract 10 (base 10) to see if there is a carry.
bmi no_carry
mov r7, #1 ; set the carry
b roll_to_next_digit
no_carry
mov r7, #0 ; set carry to zero
add r4, r4, #10 ; Add the 10 back in as there was no carry needed.
roll_to_next_digit
orr r3, r3, r4 ; Add thise digits into the sum.
ror r0, #4
ror r1, #4
ror r3, #4
subs r8, r8, #1 ; Decrement digit counter
bne loop ; If it isn't zero do the next digit.
mov r0, r3 ; Set the output registers. r0 is result. r1 is carry.
mov r1, r7
ldmfd sp!, {r4-r8,pc}
END
- GPIO Example
;---------------------------------------------------------------------------
;
; Programmer : Larry Aamodt
;
; File name : shell_2148.s
; Class : CPTR-215
; Language : ARM assembly
; Assembler : Keil
; Target MCU : NXP LPC-2148 on Embedded Artists board
; Date Written: 11/30/09
; change history: 11/30/09 LDA Updated with hardware start-up
; 12/03/09 LDA PWM register definitions added
; Description :
;
; Inputs :
;
; Outputs :
;
; Special :
; requirements
;
;
; NOTES:
;
;
;
;---------------------------------------------------------------------------
; Put application program definitions (i.e. equates) here:
; Standard definitions of Mode bits and Interrupt (I & F) flags in PSRs
Mode_USR EQU 0x10
Mode_FIQ EQU 0x11
Mode_IRQ EQU 0x12
Mode_SVC EQU 0x13
Mode_ABT EQU 0x17
Mode_UND EQU 0x1B
Mode_SYS EQU 0x1F
I_Bit EQU 0x80 ; when I bit is set, IRQ is disabled
F_Bit EQU 0x40 ; when F bit is set, FIQ is disabled
; Memory addresses for standard GPIO definitions
IO0PIN EQU 0xE0028000
IO0SET EQU 0xE0028004
IO0DIR EQU 0xE0028008
IO0CLR EQU 0xE002800C
; Memory addresses for Pulse Width Modulation (PWM)
PWM_TCR EQU 0xE0014004 ; PWM_TCR Timer Control Register
PWM_PR EQU 0xE001400C ; PWM_PR Prescaler Register
PWM_MCR EQU 0xE0014014 ; PWM_MCR Match Control Register
PWM_MR0 EQU 0xE0014018 ; PWM_MR0 Match Register 0 (sets pulse period)
PWM_MR4 EQU 0xE0014040 ; PWM_MR4 Match Register 4 (sets pulse length)
PWM_MR6 EQU 0xE0014048 ; PWM_MR6 Match Register 6 (sets pulse length)
PWM_PCR EQU 0xE001404C ; PWM_CR Control Register
PWM_LER EQU 0xE0014050 ; PWM_LER Latch Enable Register
PINSEL0 EQU 0xE002C000 ; Pin connect block - port 0
PINSEL1 EQU 0xE002C004 ; Pin connect block - port 1
; Stack size definitions
UND_Stack_Size EQU 0x00000000
SVC_Stack_Size EQU 0x00000008
ABT_Stack_Size EQU 0x00000000
FIQ_Stack_Size EQU 0x00000000
IRQ_Stack_Size EQU 0x00000080
USR_Stack_Size EQU 0x00000400
ISR_Stack_Size EQU (UND_Stack_Size + SVC_Stack_Size + ABT_Stack_Size + \
FIQ_Stack_Size + IRQ_Stack_Size)
AREA STACK, NOINIT, READWRITE, ALIGN=3
Stack_Mem SPACE USR_Stack_Size
__initial_sp SPACE ISR_Stack_Size
Stack_Top
; Area Definition and Entry Point
; Startup Code must be linked first at Address at which it expects to run.
AREA RESET, CODE, READONLY
ARM
; Exception Vectors
; Mapped to Address 0.
; Absolute addressing mode must be used.
; Dummy Handlers are implemented as infinite loops which can be modified.
Vectors LDR PC, Reset_Addr
LDR PC, Undef_Addr
LDR PC, SWI_Addr
LDR PC, PAbt_Addr
LDR PC, DAbt_Addr
NOP ; Reserved Vector
; LDR PC, IRQ_Addr
LDR PC, [PC, #-0x0FF0] ; Vector from VicVectAddr
LDR PC, FIQ_Addr
Reset_Addr DCD Reset_Handler
Undef_Addr DCD Undef_Handler
SWI_Addr DCD SWI_Handler
PAbt_Addr DCD PAbt_Handler
DAbt_Addr DCD DAbt_Handler
DCD 0 ; Reserved Address
IRQ_Addr DCD IRQ_Handler
FIQ_Addr DCD FIQ_Handler
Undef_Handler B Undef_Handler
SWI_Handler B SWI_Handler
PAbt_Handler B PAbt_Handler
DAbt_Handler B DAbt_Handler
IRQ_Handler B IRQ_Handler
FIQ_Handler B FIQ_Handler
; Reset Handler
EXPORT Reset_Handler
Reset_Handler
; Setup Stack for each mode
LDR R0, =Stack_Top
; Enter Undefined Instruction Mode and set its Stack Pointer
MSR CPSR_c, #Mode_UND:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #UND_Stack_Size
; Enter Abort Mode and set its Stack Pointer
MSR CPSR_c, #Mode_ABT:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #ABT_Stack_Size
; Enter FIQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_FIQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #FIQ_Stack_Size
; Enter IRQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_IRQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #IRQ_Stack_Size
; Enter Supervisor Mode and set its Stack Pointer
MSR CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #SVC_Stack_Size
; Enter User Mode and set its Stack Pointer
MSR CPSR_c, #Mode_USR
MOV SP, R0
SUB SL, SP, #USR_Stack_Size
; User program code goes here
main
ldr sp, = Stack_Mem ; load stack pointer
ldr r1, =PINSEL0
mov r0, #0 ; set P0.0 to P0.15 as GPIO
str r0,[r1]
ldr r1, =IO0DIR ; Get ready to set direction of data
ldr r0, =0xffff ; output
str r0, [r1] ; set the direction
ldr r1, =IO0PIN ; load the address of the port0
mov r0, #0
next
str r0, [r1]
add r0, r0, #1
ldr r2, =0x200
delay
subs r2,r2,#1
bne delay
b next
AREA Thedata, DATA, READWRITE
ALIGN
datastart EQU 0x40000004
SPACE 20
;FILL 20, 0xff ; Why is this stored at 0x50 instead of 0x58?
; Or maybe a better question: How do I set data at
; a specific memory location?
END
- LCD Example
;---------------------------------------------------------------------------
;
; Programmer : Larry Aamodt
;
; File name : shell_2148.s
; Class : CPTR-215
; Language : ARM assembly
; Assembler : Keil
; Target MCU : NXP LPC-2148 on Embedded Artists board
; Date Written: 11/30/09
; change history: 11/30/09 LDA Updated with hardware start-up
; 12/03/09 LDA PWM register definitions added
; Description :
;
; Inputs :
;
; Outputs :
;
; Special :
; requirements
;
;
; NOTES:
;
;
;
;---------------------------------------------------------------------------
; Put application program definitions (i.e. equates) here:
; Standard definitions of Mode bits and Interrupt (I & F) flags in PSRs
Mode_USR EQU 0x10
Mode_FIQ EQU 0x11
Mode_IRQ EQU 0x12
Mode_SVC EQU 0x13
Mode_ABT EQU 0x17
Mode_UND EQU 0x1B
Mode_SYS EQU 0x1F
I_Bit EQU 0x80 ; when I bit is set, IRQ is disabled
F_Bit EQU 0x40 ; when F bit is set, FIQ is disabled
; Memory addresses for standard GPIO definitions
IO0PIN EQU 0xE0028000
IO0SET EQU 0xE0028004
IO0DIR EQU 0xE0028008
IO0CLR EQU 0xE002800C
; Memory addresses for Pulse Width Modulation (PWM)
PWM_TCR EQU 0xE0014004 ; PWM_TCR Timer Control Register
PWM_PR EQU 0xE001400C ; PWM_PR Prescaler Register
PWM_MCR EQU 0xE0014014 ; PWM_MCR Match Control Register
PWM_MR0 EQU 0xE0014018 ; PWM_MR0 Match Register 0 (sets pulse period)
PWM_MR4 EQU 0xE0014040 ; PWM_MR4 Match Register 4 (sets pulse length)
PWM_MR6 EQU 0xE0014048 ; PWM_MR6 Match Register 6 (sets pulse length)
PWM_PCR EQU 0xE001404C ; PWM_CR Control Register
PWM_LER EQU 0xE0014050 ; PWM_LER Latch Enable Register
PINSEL0 EQU 0xE002C000 ; Pin connect block - port 0
PINSEL1 EQU 0xE002C004 ; Pin connect block - port 1
; Stack size definitions
UND_Stack_Size EQU 0x00000000
SVC_Stack_Size EQU 0x00000008
ABT_Stack_Size EQU 0x00000000
FIQ_Stack_Size EQU 0x00000000
IRQ_Stack_Size EQU 0x00000080
USR_Stack_Size EQU 0x00000400
ISR_Stack_Size EQU (UND_Stack_Size + SVC_Stack_Size + ABT_Stack_Size + \
FIQ_Stack_Size + IRQ_Stack_Size)
AREA STACK, NOINIT, READWRITE, ALIGN=3
Stack_Mem SPACE USR_Stack_Size
__initial_sp SPACE ISR_Stack_Size
Stack_Top
; Area Definition and Entry Point
; Startup Code must be linked first at Address at which it expects to run.
AREA RESET, CODE, READONLY
ARM
; Exception Vectors
; Mapped to Address 0.
; Absolute addressing mode must be used.
; Dummy Handlers are implemented as infinite loops which can be modified.
Vectors LDR PC, Reset_Addr
LDR PC, Undef_Addr
LDR PC, SWI_Addr
LDR PC, PAbt_Addr
LDR PC, DAbt_Addr
NOP ; Reserved Vector
; LDR PC, IRQ_Addr
LDR PC, [PC, #-0x0FF0] ; Vector from VicVectAddr
LDR PC, FIQ_Addr
Reset_Addr DCD Reset_Handler
Undef_Addr DCD Undef_Handler
SWI_Addr DCD SWI_Handler
PAbt_Addr DCD PAbt_Handler
DAbt_Addr DCD DAbt_Handler
DCD 0 ; Reserved Address
IRQ_Addr DCD IRQ_Handler
FIQ_Addr DCD FIQ_Handler
Undef_Handler B Undef_Handler
SWI_Handler B SWI_Handler
PAbt_Handler B PAbt_Handler
DAbt_Handler B DAbt_Handler
IRQ_Handler B IRQ_Handler
FIQ_Handler B FIQ_Handler
; Reset Handler
EXPORT Reset_Handler
Reset_Handler
; Setup Stack for each mode
LDR R0, =Stack_Top
; Enter Undefined Instruction Mode and set its Stack Pointer
MSR CPSR_c, #Mode_UND:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #UND_Stack_Size
; Enter Abort Mode and set its Stack Pointer
MSR CPSR_c, #Mode_ABT:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #ABT_Stack_Size
; Enter FIQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_FIQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #FIQ_Stack_Size
; Enter IRQ Mode and set its Stack Pointer
MSR CPSR_c, #Mode_IRQ:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #IRQ_Stack_Size
; Enter Supervisor Mode and set its Stack Pointer
MSR CPSR_c, #Mode_SVC:OR:I_Bit:OR:F_Bit
MOV SP, R0
SUB R0, R0, #SVC_Stack_Size
; Enter User Mode and set its Stack Pointer
MSR CPSR_c, #Mode_USR
MOV SP, R0
SUB SL, SP, #USR_Stack_Size
; User program code goes here
main
bl lcdReset ; set up the lcd
bl lcdClear
mov r0, #32
loop
bl lcdWRdata ; write to the LCD
add r0, r0, #1 ; increment the data
mov r9, r0
ldr r0, =1000000
bl delay
mov r0, r9
b loop
; User data area definition follows
AREA appdata, DATA, NOINIT, READWRITE
;-----------------------------------------------------------------------------
; Copyright (C) 2012 ....
;
; Programmer : Larry Aamodt
;
; File name : lcd_routines.asm
; Language : ARM assembly
; Assembler ; Keil
; Target MCU : NXP LPC2148 on Embedded Artists education board
; Date : 12/05/12 LDA lcd_routines.asm. debugged
;
; Description : LCD display routines
; Copy this code to your own program
;
; Procedures you can call are:
; lcdReset must be called first. no parameters.
; lcdClear use to clear the display & home the cursor
; no parameters are required.
; lcdWRdata use to write one character on the display
; place an ASCII char in r0 before calling.
; The cursor will advance.
; lcdCursorAt use to move the cursor. Two parameters
; r0 = row (1 or 2)
; r1 = column to move cursor to (0-15)
;
; Example use of the LCD routines:
; bl lcdReset ; do this once at the top of your program
;
; mov r0,#31h ; place the ascii code for number one in r0
; bl lcdWRdata ; display the character '1' on LCD display
;
; bl lcdClear ; clear the display
;
; mov r0,#1 ; select LCD row 1
; mov r1,#4 ; select LCD column 4
; bl lcdCursorAt ; move the cursor
;
;
; NOTE: All registers are saved by these routines, i.e. upon return
; from the subroutine all registers, except flags, have the
; same value in them as before the subroutine was called (this
; breaks with the ARM convention for subroutines but is done
; to make it easier for you).
;
;-----------------------------------------------------------------------------
AREA lcdroutines,CODE,READONLY
EXPORT lcdReset
EXPORT lcdClear
EXPORT lcdWRdata
EXPORT lcdCursorAt
EXPORT delay
; -----------------------------------------------------------------------------
; LCD Procedures follow.
;------------------------------------------------------------------------------
; ***** LCD equates ******
;IO0PIN EQU 0xE0028000
;IO0SET EQU 0xE0028004
;IO0DIR EQU 0xE0028008
;IO0CLR EQU 0xE002800C
IO1PIN EQU 0xE0028010
IO1SET EQU 0xE0028014
IO1DIR EQU 0xE0028018
IO1CLR EQU 0xE002801C
T0_TCR_ADDR EQU 0xE0004004
T0_PR_ADDR EQU 0xE000400C
T0_MCR_ADDR EQU 0xE0004014
T0_MR0_ADDR EQU 0xE0004018
; -----------------------------------------------------------------------------
; Procedure lcdReset Must be called before writing to the LCD
; No parameters required
; -----------------------------------------------------------------------------
lcdReset STMFD SP!,{LR,r0,r1,r2,r3,r4,r5,r6,r7,r8,r9}
LDR r1,=T0_PR_ADDR ; Prescale register
MOV r2,#2 ; prescale count value
STR r2,[r1] ; Prescaler will divide by 3
LDR r1,=T0_MCR_ADDR ; Match control register
MOV r2,#0x6 ; bit 2 = one
STR r2,[r1] ; stop counter when match reached
LDR r5,=IO0CLR
LDR r6,=IO0SET
LDR r7,=IO1CLR
LDR r8,=IO1SET
LDR r0,=35000
BL delay ; delay 35ms
LDR r0,=IO0DIR
LDR r4,[r0] ; read current Port 0 direction bits
LDR r3,=0x40408000 ; one's for pins to be set for output
ORR r4,r4,r3 ; bits 22 & 30 to be outputs
STR r4,[r0] ; set lcd port bits to output
LDR r3,=0x00400000 ;
STR r3,[r5] ; write 0 to LCD R/W signal
LDR r3,=0x40008000
STR r3,[r6] ; turn on backlight - write 1 to P0.30
LDR r0,=IO1DIR
LDR r4,[r0] ; read current Port 1 direction bits
LDR r3,=0x03FF0000 ; one's for lcd pins - set for output
ORR r4,r4,r3 ; bits 16 to 25 to be outputs
STR r4,[r0] ; set lcd port direction bits to output
STR r3,[r7] ; clear the LCD data & control bits
LDR r9,=0x02000000 ; bit pattern to turn on/off E
LDR r2,=0x00380000 ; function: 2 lines, 5x7 dots
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
MOV r0,#40
BL delay ; wait 40 microseconds
LDR r2,=0x000E0000 ; function: display on, cursor on
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
MOV r0,#40
BL delay ; wait 40 microseconds
LDR r2,=0x00010000 ; lcd function: clear display
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
MOV r0,#1600
BL delay ; delay for 1600 microseconds
LDR r2,=0x00030000 ; lcd function: set entry mode
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
end_lcdReset LDMFD SP!,{PC,r0,r1,r2,r3,r4,r5,r6,r7,r8,r9}
;------------------------------------------------------------------------------
; Procedure pulse_e uses r0. Not interuptable (r14 not saved)
; assumes r9 has 0x02000000 in it
; assumes r7 has IO1CLR address in it
; assumes r8 has IO1SET address in it
;------------------------------------------------------------------------------
pulse_e MOV r0,#4
STR r9,[r8] ; assert E
ploop1 SUBS r0,r0,#1 ; delay 600ns or so
BNE ploop1
STR r9,[r7] ; de-assert E
MOV r0,#8
ploop2 SUBS r0,r0,#1 ; delay 1100ns or so
BNE ploop2
end_pulse_e BX LR
; -----------------------------------------------------------------------------
; Procedure lcdClear Clears the LCD and positions cursor to line1, left col
; no parameters required
; -----------------------------------------------------------------------------
lcdClear STMFD SP!,{LR,r0,r1,r2,r3,r7,r8,r9}
LDR r9,=0x02000000 ; bit pattern to turn on/off E
LDR r3,=0x03FF0000 ; one's for pins used for lcd
LDR r7,=IO1CLR
LDR r8,=IO1SET
LDR r2,=0x00010000 ; lcd function: clear display
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
MOV r0,#1600
BL delay
end_lcdClear LDMFD SP!,{PC,r0,r1,r2,r3,r7,r8,r9}
; -----------------------------------------------------------------------------
; Procedure lcdCursorAt
; r0 assumed to contain the row# (1 or 2)
; r1 assumed to contain col#(0-15)
; No cursor movement if invalid row or col # is found
; -----------------------------------------------------------------------------
lcdCursorAt STMFD SP!,{LR,r0,r1,r2,r3,r7,r8,r9}
CMP r1,#15 ; check column & row range
BHI end_lcdCursorAt
CMP r0,#0
BEQ end_lcdCursorAt
CMP r0,#2
BHI end_lcdCursorAt
ADDEQ r1,r1,#0x40 ; build the cursor address
LDR r0,=0x00800000
ORR r2,r0,r1,LSL #16 ; r2 now has the address
LDR r3,=0x03FF0000 ; one's for pins used for lcd
LDR r7,=IO1CLR
LDR r8,=IO1SET
LDR r9,=0x02000000 ; bit pattern to turn on/off E
STR r2,[r8] ; set lcd function bits
BL pulse_e
STR r3,[r7] ; clear lcd bits
MOV r0,#40
BL delay
end_lcdCursorAt LDMFD SP!,{PC,r0,r1,r2,r3,r7,r8,r9}
; -----------------------------------------------------------------------------
; Procedure lcdWRdata Writes data (an ASCII character) to the
; current cursor position on the LCD
; r0 is assumed to contain the character to send
; -----------------------------------------------------------------------------
lcdWRdata STMFD SP!,{LR,r0,r1,r2,r3,r7,r8,r9}
LDR r9,=0x02000000 ; bit pattern to turn on/off E
LDR r3,=0x03FF0000 ; one's for pins used for lcd
LDR r7,=IO1CLR
LDR r8,=IO1SET
AND r0,r0,#0xFF ; make sure only 8 bits are non-zero
ORR r0,r0,#0x100 ; set bit that indicates writing
LSL r0,r0,#16
STR r0,[r8] ; write data
BL pulse_e
STR r3,[r7] ; clear lcd bits
end_lcdWRData LDMFD SP!,{PC,r0,r1,r2,r3,r7,r8,r9}
; -----------------------------------------------------------------------------
; Procedure delay microsecond delay using timer 0
; (12Mhz clock & VPB divide by 4 assumed)
; reg R0 must contain a delay value in uS
; Not interruptable (r14 not saved)
; assumes lcdReset has been called prior to delay
; r0, r1 not preserved
; -----------------------------------------------------------------------------
delay LDR r1,=T0_MR0_ADDR ; Match register zero
STR r0,[r1] ; load match count per R0
; ldr r0,=0x8000
; str r0,[r5] ; turn on p0.15 led
LDR r1,=T0_TCR_ADDR ; Timer 0 Control Register
MOV r0,#2 ; bit 1 = one
STR r0,[r1] ; Clear counter & prescaler
MOV r0,#0
STR r0,[r1]
MOV r0,#1 ; bit 0 = one
STR r0,[r1] ; Turn on counter
dloop LDR r0,[r1] ; Read TCR register
ANDS r0,r0,#1
BNE dloop
; ldr r0,=0x8000
; str r0,[r6] ; turn off p0.15 led
end_delay BX LR ; Return
END