View source for 8bit Printer Port (Paul Bauriedl)

This [[8bit Printer Ports|8bit Printer Port]] expansion is described in the book [[Maschinenspracheprogramme und Hardware-Erweiterungen für Schneider CPC's]] by [[Paul Bauriedl]]. It connects externally to the 7bit printer port (and the 5V power supply) of the CPC and doesn't require any internal modifications to the CPC.

== Description ==

In this design, only the lower 4 bits of the printer port are directly connected to the printer. The upper 4 bits are generated with the help of a latch (LS 75). If you want to print, you have to send the upper 4 bits in D0-D3 and set D4 to high to buffer the values in the latch which is connected to D4-D7 of the printer. The rest of the data can be sent by the normal printer routine of the firmware (with D4 set to 0 to disable the latch).

== Schematics ==

[[Image:8bitPrinterPortPaulBauriedl.png]]]

== Listing ==

<pre>
10 ;Patch fuer 8-bit Centronics
20 ;direkt unter HIMEM (+Floppy)
30 ;
40 indjmp: 	equ	#bdf1
50 ;
60		org	42619-40
70 ;Initialisieren
80 		ld	hl, (indjmp+1)
90		ld	(retour+1),hl
100		ld	hl,bit0
110		ld	(indjmp+1),hl
120		ret
130 ;
140 ;neue Ausgaberoutine
150 ;ist ueber Druckerindirektion
160 ;#BDF1 eingeschleift
170 ;
180 bit0:	ld	b,#ef
190		push	af
200		srl	a
210		srl	a
220		srl	a
230		srl	a
240		out	(c),a
250		set	4,a
260		out	(c),a
270		res	4,a
280		out	(c),a
290		pop	af
300		and	#0f
310 ;Jump wird beruecksichtigt
320 ;je nach System!
330 retour:	jp	#07f8
</pre>

[[Category:Printers and printer ports]] [[Category:DIY]]