6850 ACIA support

6850.asm

@@ -0,0 +1,83 @@
+; 6502 BIOS 
+; Based on original code by Daryl Rictor
+; Adapted to 6850 ACIA board for RC2014
+; NOTE: The 6850 ACIA works with the 6502 card for simple Monitor functions
+; However, loading an Intel HEX file appears to overwhelm the ACIA.
+;
+;
+; ----------------- assembly instructions ---------------------------- 
+;
+; this is a subroutine library only
+; it must be included in an executable source file
+;
+;
+;*** I/O Locations *******************************
+; Define the i/o address of the UART chip
+;*** 6850 ACIA ************************
+
+uart_base       = $c080
+uart_reg0       = $c080
+uart_reg1       = $c081
+uart_xmit       = uart_reg1     ; Used by upload.asm
+
+;
+;***********************************************************************
+; UART I/O Support Routines
+; We'll use Daryl's routine names for compatibility with his software/code
+; Otherwise, we'll use UART-agnostic nomemclature
+
+;---------------------------------------------------------------------
+;
+ 
+ACIA1_init
+uart_init
+                lda     #$03    ; master reset
+                sta     uart_reg0
+		; 0001 0110
+;                lda     #$16    ; 28.8k baud, /64, 8+1, rts=0, no interrupts
+		; 0001 0101
+                lda     #$15    ; 115200 baud, /16, 8+1, rts=0, no interrupts
+
+                sta     uart_reg0
+                rts                     ; done
+                
+;---------------------------------------------------------------------
+; Input char from UART (blocking)
+; Exit: character in A
+ACIA1_Input
+uart_input
+               lda      uart_reg0           ; Serial port status             
+               and      #$01               ; is recvr full
+               beq      uart_input        ; no char to get
+               lda      uart_reg1           ; get chr
+               rts                      ;
+
+;---------------------------------------------------------------------
+; Non-waiting get character routine 
+; Scan for input (no wait), C=1 char, C=0 no character
+ACIA1_Scan
+uart_scan
+                clc
+                lda   uart_reg0        ; Serial port status
+                and   #$01               ; mask rcvr full bit
+                beq   uart_scan2
+                lda   uart_reg1           ; get chr
+                sec
+uart_scan2     rts
+
+;---------------------------------------------------------------------
+; output to OutPut Port
+; Entry: character in A
+; Exit: character in A
+ACIA1_Output
+uart_output   
+                pha                      ; save registers
+uart_out1     
+                lda   uart_reg0           ; serial port status
+                and   #$02               ; is tx buffer empty
+                beq   uart_out1         ; no
+                pla                      ; get chr
+                sta   uart_reg1           ; put character to Port
+                rts                      ; done
+;
+;end of file