WriteString and initial serial

1 files changed, 75 insertions, 22 deletions

diff --git a/cmpen472hw5_McDonnell/Sources/main.asm b/cmpen472hw5_McDonnell/Sources/main.asm
index 55f7e17..06b44c8 100644
--- a/cmpen472hw5_McDonnell/Sources/main.asm
+++ b/cmpen472hw5_McDonnell/Sources/main.asm
@@ -57,6 +57,15 @@ DDRA        equ         $0002           ; data direction register for PORTA
 PORTB       equ         $0001           ; i/o port B addresses
 DDRB        equ         $0003           ; data direction register for PORTB
 
+SCIBDH      equ         $00C8           ; Serial port (SCI) Baud Register H
+SCIBDL      equ         $00C9           ; Serial port (SCI) Baud Register L
+SCICR2      equ         $00CB           ; Serial port (SCI) Control Register 2
+SCISR1      equ         $00CC           ; Serial port (SCI) Status Register 1
+SCIDRL      equ         $00CF           ; Serial port (SCI) Data Register
+
+CR          equ         $0d             ; carriage return, ASCII 'Return' key
+LF          equ         $0a             ; line feed, ASCII 'next line' character
+
 **************************************************************************
 * Data Section: address used [ $3000 to $30FF ] RAM Memory
 *
@@ -66,7 +75,7 @@ Counter     dc.w        $0036           ; X register count number for time Delay
                                         ;   loop for 10 useconds
                                         ; The work to calculate this number is in
                                         ; the comments for the delay10usec subroutine.
-                                        
+
 LEVEL       dc.b        $0005           ; Light Level that the LED should be
 
 *
@@ -80,22 +89,6 @@ pgstart     lds         #$3100          ; initialize the stack pointer
             staa        DDRB            ; set PORTB bit 4,5,6,7 as output
 
 mainLoop
-            ldaa        #1
-            jsr         TurnOnLED
-            ldaa        #2
-            jsr         TurnOnLED
-            ldaa        #3
-            jsr         TurnOnLED
-            ldaa        #1
-            jsr         TurnOffLED
-            ldaa        #2
-            jsr         TurnOffLED
-            ldaa        #3
-            jsr         TurnOffLED
-            jsr         HighToLow
-            jsr         HighToLow
-            jsr         LowToHigh
-            jsr         LowToHigh
             bra         mainLoop        ; Loop back to mainLoop always
 
 **************************************************************************
@@ -103,6 +96,28 @@ mainLoop
 *
 
 ;*************************************************************************
+; WriteString subroutine
+;
+; This subroutine will write a given null terminated string to the serial.
+;
+; Input:                   Address of null terminated string in X
+; Output:                  Null terminated string written to serial
+; Registers in use:        X for the address of the string and A for the current byte
+; Memory locations in use: Memory Address for serial line, address of the string
+;
+; Comments: This subroutine requires serial to be setup and putchar subroutine.
+;
+
+WriteString
+            psha                        ; Save A to the stack
+writeLoop   ldaa       1,x+             ; Load the byte at addr in X, then add 1
+            beq        doneWrite        ; if A == 0, branch to doneWrite
+            jsr        putchar          ; Jump to putchar to write byte to serial
+            bra        writeLoop        ; branch always to writeLoop
+doneWrite   pula                        ; restore A from the stack
+            rts                         ; return to caller
+
+;*************************************************************************
 ; TurnOnLED subroutine
 ;
 ; This subroutine will dim turn on a specified LED
@@ -124,7 +139,7 @@ onCheckTwo cmpa         #2              ; Compare A to 2
            bne          onCheckThr      ; If A != 2, check next number
            bset         PORTB,%00100000 ; Turn On LED 2
            bra          onDone          ; Jump to onDone
-onCheckThr bset         PORTB,%01000000 ; Turn On LED 3 
+onCheckThr bset         PORTB,%01000000 ; Turn On LED 3
 onDone     rts                          ; Return to caller
 
 ;*************************************************************************
@@ -149,7 +164,7 @@ ofCheckTwo cmpa         #2              ; Compare A to 2
            bne          ofCheckThr      ; If A != 2, check next number
            bclr         PORTB,%00100000 ; Turn Off LED 2
            bra          ofDone          ; Jump to onDone
-ofCheckThr bclr         PORTB,%01000000 ; Turn Off LED 3 
+ofCheckThr bclr         PORTB,%01000000 ; Turn Off LED 3
 ofDone     rts                          ; Return to caller
 
 ;*************************************************************************
@@ -178,7 +193,7 @@ decrease    tbeq        A,doneDec       ; Test if A == 0, skip loop if so
             bra         decrease        ; loop to decrease always
 doneDec     pula                        ; Restore A from the stack
             rts                         ; Return to caller
-            
+
 ;*************************************************************************
 ; HighToLow subroutine
 ;
@@ -252,9 +267,9 @@ doneLoop    pula                        ; restore A from the stack
 ; Comments: Code relies on counter being $39 to be exactly 10 usec work is below
 ; Given: freq = 24MHz = 24000000     sec = 10 usec = 0.00001
 ; freq = cycles / seconds
-; 
+;
 ; cycles = freq * seconds = 24000000Hz * 0.00001 = 240
-; 
+;
 ; This sub routine is 12 + 4 * 'Counter' cycles long, solving for 'Counter'
 ; the result is found to be 57.
 ;
@@ -268,5 +283,43 @@ innerLoop   dex                         ; decrement register x by 1
             nop                         ; extra nop to make exactly 10 usec
             rts                         ; return to caller
 
+;***************putchar************************
+;* Program: Send one character to SCI port, terminal
+;* Input:   Accumulator A contains an ASCII character, 8bit
+;* Output:  Send one character to SCI port, terminal
+;* Registers modified: CCR
+;* Algorithm:
+;    Wait for transmit buffer become empty
+;      Transmit buffer empty is indicated by TDRE bit
+;      TDRE = 1 : empty - Transmit Data Register Empty, ready to transmit
+;      TDRE = 0 : not empty, transmission in progress
+;**********************************************
+putchar        brclr SCISR1,#%10000000,putchar   ; wait for transmit buffer empty
+               staa  SCIDRL                      ; send a character
+               rts
+;***************end of putchar*****************
+
+
+;****************getchar***********************
+;* Program: Input one character from SCI port (terminal/keyboard)
+;*             if a character is received, other wise return NULL
+;* Input:   none
+;* Output:  Accumulator A containing the received ASCII character
+;*          if a character is received.
+;*          Otherwise Accumulator A will contain a NULL character, $00.
+;* Registers modified: CCR
+;* Algorithm:
+;    Check for receive buffer become full
+;      Receive buffer full is indicated by RDRF bit
+;      RDRF = 1 : full - Receive Data Register Full, 1 byte received
+;      RDRF = 0 : not full, 0 byte received
+;**********************************************
+getchar        brclr SCISR1,#%00100000,getchar7
+               ldaa  SCIDRL
+               rts
+getchar7       clra
+               rts
+;****************end of getchar****************
+
             end                         ; last line of the file