implement $EA7E entry point and fix $EA31 entry point. Issue #20

c64/kernal/ea31.default_irq_handler.s

@@ -0,0 +1,7 @@
+default_irq_handler:	
+
+	jsr blink_cursor
+	jsr scan_keyboard
+
+	;; Acknowledge CIA interrupt and return
+	jmp clear_cia1_interrupt_flag_and_return_from_interrupt:

c64/kernal/ea7e.s

@@ -0,0 +1,11 @@
+	;; https://csdb.dk/forums/index.php?roomid=11&topicid=5776
+	;; Clear the CIA1 interrupt flag, and then fall through to
+	;; the return from interrupt routine
+
+clear_cia1_interrupt_flag_and_return_from_interrupt:
+
+	;; We have free choice of LDA, LDX or LDY to achieve this goal
+	;; in 3 bytes and minimum cycles. Thus we randomly choose LDY.
+	LDY $DC0D
+
+	;; FALL THROUGH to $EA81

c64/kernal/ioinit.s

@@ -15,6 +15,11 @@ ioinit:
 	sta $D020
 	sta $D021
 
+	;; Turn off sprites
+	;; (observed hanging around after running programs and resetting)
+	lda #$00
+	sta $D015
+	
 	;; Enable CIA1 IRQ and ~50Hz timer
 	;; (https://csdb.dk/forums/?roomid=11&topicid=69037)
 	lda #$7f

c64/kernal/irq_handler.s

@@ -15,18 +15,9 @@ irq_handler:
 	tya
 	pha
 
-	;; Acknowledge CIA interrupt
-	lda $dc0d
-	
 	;; Call interrupt routine
 	;; (but only if initialised)
 	lda $0314
 	ora $0315
 	beq default_irq_handler
 	jmp ($0314)
-default_irq_handler:	
-
-	jsr blink_cursor
-	jsr scan_keyboard
-
-	jmp return_from_interrupt

src/preprocess.c

@@ -119,6 +119,7 @@ int main(int argc,char **argv)
       if (sscanf(source_files[i].file,"%x.%[^.]",&addr,funcname)==2) {
 	// Function must appear at specific address
 	source_files[i].address=addr;
+	printf("function '%s' should be placed at $%04X\n",funcname,addr);
       }
     }