Block loader for TT2500.

The 2500 bootstrap ROM expects to receive a block loader first, which
will run and recieve the actual payload which is the microcode and
font data divided into blocks.

src/danny/loader.24

@@ -0,0 +1,74 @@
+(SETQ  LOADER '(
+
+	(CALL 0 WD)
+	(CALL 1 ADR)
+	(CALL 2 CNT)
+	(CALL 3 CHK)
+	(CALL 4 TYP)
+	(CALL 124 OK-CHR)
+	(CALL 106 LOOSE-CHR)
+
+START		(GET 	WD IN 	& RESET TTY)
+		(SUB	WD WD)
+WAIT-FLAG	(PUSHJ 	CHR-IN)
+		(GET	WD WD 	& TO SEE IT)
+		(BMC	WAIT-FLAG & WAIT FOR FLAG)
+		(SUB	CHK CHK)
+		(PUSHJ	GET-WD)
+		(GET	TYP WD)
+		(BEQ	EXECUTE	& TYPE 0 IS EXECUTE)
+		(PUSHJ	GET-WD)
+		(GET 	ADR WD  & START ADDRESS)
+		(GET	XR ADR)
+		(PUSHJ	GET-WD)
+		(GET 	CNT WD & NUMBER OF WORDS)
+		(DEC	TYP)
+		(BEQ	CRM-LOOP & TYPE 1 IS LOAD CRM)
+		(DEC	TYP)
+		(BEQ	MEM-LOOP & TYPE 2 IS LOAD MEM)
+		(JUMP	LOOSE)
+MEM-LOOP	(PUSHJ	GET-WD)
+		(IWRITE	ADR WD)
+		(DEC	CNT)
+		(BPL	CRM-LOOP)
+		(JUMP	END)
+EXECUTE		(PUSHJ	GET-WD)
+		(LOD	7)
+		(JUMP-PLACE)
+		(GET	XR 7)
+		(LCM	WD)
+JUMP-PLACE	(0 	& WORD TO BE EXECUTED IS PUT HERE)
+		(JUMP	END)
+CRM-LOOP	(PUSHJ	GET-WD)
+		(LCM	WD)
+		(DEC	CNT)
+		(BPL	CRM-LOOP)
+END		(PUSHJ	GET-WD)
+		(GET	CHK CHK & LOOK AT CHECK SUM)
+		(BNE	LOOSE)
+		(LOD	7)
+		(OK-CHR)
+CONFIRM		(PUT	7 UART)
+		(NOP	7 	& UARTS ARE SLOW)
+		(NOP	7	& VERY SLOW)
+		(JUMP	START)
+GET-WD		(PUSHJ	CHR-IN)
+		(PUSHJ	CHR-IN)
+		(PUSHJ	CHR-IN)
+		(PUSHJ	CHR-IN)
+		(ADD	CHK WD)
+		(POPJ)
+CHR-IN		(DIS	INT2 1 0)
+		(JUMP	CHR-IN)
+		(GET	5 IN)
+		(ANDI	WD WD )
+		(7777)
+		(ROT	WD WD 14)
+		(ANDI	5 5 )
+		(17)
+		(IOR	WD 5)
+		(POPJ)
+LOOSE		(LOD	7)
+		(LOOSE-CHR)
+		(JUMP 	CONFIRM)
+))