Reprom64

Kombinierter ROM-Ersatz für den C64

Reprom64 Rev.3

Das Reprom64 ist ein Multirom-Adapter für den C64, mit dessen Hilfe alle ROM-Bausteine durch ein einziges 64kb großes 27C512-Eprom ersetzt werden können. Das Eprom bietet Platz für vier Kernal, vier Zeichensätze und zwei Basic-ROMs. Eine beliebige Auswahl aus diesen ROMs kann mit Hilfe der Kontrollleitungen eingestellt werden. Ein GAL16V8 dekodiert die Chip-Select-Signale der einzelnen ROM-Bausteine des C64 und addressiert das Eprom entsprechend.

Im Hinblick auf die ROM-Bausteine des C64 gibt es zwei verschiedene Typen von Hauptplatinen: auf den älteren Revisionen bis einschließlich Assy. 250466 sind drei getrennte 24-Pin ROM-Bausteine direkt nebeneinander verbaut. Auf den neueren Revisionen mit der Assy. 250469 sind Kernal und Basic in einem einzigen 28-Pin Baustein zusammengefasst, während sich das Zeichensatz-ROM weiterhin in einem 24-Pin-Baustein links davon befindet. Zudem unterscheiden sich die einzelnen Revisionen mitunter deutlich in den Abständen der Bausteine untereinander.

Die Platine des Reprom64 eignet sich jedoch für alle C64 Hauptplatinen. Die Platine kann für einen bestimmten Hauptplatinentyp aufgebaut werden, indem die Adapterleisten und Drahtbrücken auf unterschiedliche Weise eingelötet werden.

Auf den älteren Hauptplatinen wird das Reprom64 in den mittig gelegenen Kernal-Sockel gesteckt und greift mit Hilfe zusätzlicher Adpaterpins links und rechts die benötigten Chip-Select-Signale aus dem Basic- bzw. Zeichensatz-Sockel ab.

Auf neueren Hauptplatinen wird das Reprom64 hingegen in den kombinierten Kernal- und Basic-Sockel gesetzt und greift lediglich ein zusätzliches Singal am links davon liegenden Zeichensatz-Sockel ab.

Downloads

Quellen

Die Quelltext-Distribution enthält die Quellen für den 16V8GAL Logikbaustein sowie den Schaltplan und das Platinen-Layout im KiCad-Format.

Die letzte stabile Version ist Reprom64-1.3.tar.gz.

Alle veröffentlichten Versionen finden sich unter /download/Reprom64

Neuste Entwicklungen können auf github verfolgt werden:

git clone https://github.com/hbekel/Reprom64

Fertigungsdateien

Bestellung von Bausätzen

Ich biete Bausätze zum Preis von 10€ pro Stück an. Der Bausatz enthält eine Platine, einen vorprogrammierten GAL und alle weiteren benötigten Bauteilen (außer einem Eprom, Verbindungskabeln und Schaltern). Weltweiter Versand per Post ist kostenlos.

Bestellungen könnt Ihr per Mail an henning.liebenau@protonmail.com tätigen.

Bitte verwendet das Wort “Reprom64” im Betreff. Gebt in der Mail euren vollen Namen, Eure Lieferadresse und die Anzahl der gewünschten Bausätze an. Bitte beachtet, dass die Anzahl der Bausätze pro Person auf zwei Stück beschränkt ist. Ihr bekommt dann von mir per Mail weitere Informationen zur Bezahlung per Überweisung. Bitte beachtet, dass im voraus gezahlt werden muss, um die Bestellung verbindlich zu bestätigen.

Hinweise zur Verfügbarkeit

Ich versuche stets eine ausreichende Menge an Bausätzen auf Lager zu halten. Bitte beachtet jedoch, dass dies mit geringem Budget und bei minimaler Gewinnmarge in meiner Freizeit passiert. Mein Ziel ist es primär, der Community meine Hardware zugänglich zu machen, und nicht etwa ein profitables Geschäft zu betreiben.

Sollte ich also momentan keine Bausätze auf Lager haben kann es durchaus einige Wochen dauern, bis ich eine neue Serie von Bausätzen produzieren und somit eurer Bestellung nachkommen kann. Unter Umständen muss ich auch warten, bis eine ausreichende Anzahl an Vorbestellungen eingeht, bevor ich selbst die nötigen Bauteile zu einem ausreichend günstigen Preis bestellen kann. In diesen Fällen werde ich Euch natürlich regelmäßig über den Status Eurer Bestellung informieren. Es bedarf also unter Umständen ein wenig Geduld und auch Vertrauen von Eurer Seite.

Aufbau

Abhängig von der zu verwendenen C64-Hauptplatine müssen Adapterleisten, Pfostenleisten und Drahtbrücken an unterschiedlichen Positionen eingelötet werden. Bitte wählt hier Euren gewünschten Hauptplatinen-Typ aus, um die jeweils passende Bestückung anzuzeigen:

IC-Adapterleisten für die vorhandenen Hauptplatinen-Sockel
Drahtbrücken

Die Adapterleisten werden auf der Oberseite verlötet. Alle anderen Bauteile werden auf der Unterseite verlötet.

Es wird empfohlen, zunächst alle benötigten Adapterleisten zuzuschneiden und bereits in die Hauptplatinen-Sockel zu stecken. Dann kann die Platine aufgelegt werden und die Adapterleisten können von oben verlötet werden. So wird sichergestellt, dass sich das Reprom64 später gut einsetzen lässt, ohne das sich unter Umständen vorhandene kleinere Variationen in den Sockelabständen negativ auswirken.

Die Adressbus-Signale A5 und A8 auf der rechten Seite der Platine müssen nicht verbunden werden. Die Signale werden dort lediglich an gut zugänglicher Stelle angeboten, um sie eventuell für andere Hardware-Erweiterungen nutzen zu können. So benötigen zum Beispiel Stereo-SID-Adapter diese Adresssignale.

Bauteile

Reference Type Value Package/RM
C1 Filmkondensator 100nF 2.5mm
C2 Filmkondensator 100nf 2.5mm
U1 27C512 Eprom + Sockel 64kb DIP-28
U2 GAL16V8D-15LP + Sockel - DIP-20
P1 Präzisions-Adapterleiste 40-polig 2.5mm
P2 P3 P4 Gewinkelte Pfostenleisten 2-polig 2.5mm

Aufbau des Eproms und Funktion der Kontrollleitungen

Die untenstehende Tabelle zeigt den Aufbau des Eprom-Speichers und die für die Anwahl der jeweiligen ROM-Inhalte benötigten Leitungszustände. Die Kontrollleitungen stehen an den mit BASIC, CHARSET und KERNAL beschrifteten Anschlüssen zur Verfügung, wobei Bit 1 jeweils am linken Pin und Bit 0 jeweils am rechten Pin zu finden ist. Lediglich am Anschluss für das BASIC-Rom sind beide Pins mit Bit 0 belegt.

Die Kontrolleitungen werden durch die internen Pullup-Widerstände des GALs auf HIGH-Pegel gehalten, sofern die Leitung nicht anderweitig angesteuert wird. Somit können einfache Schließer auf Masse verwendet werden, um die jeweiligen ROMs auszuwählen. Ist der Schalter geöffnet und die zugehörige Leitung damit nicht verbunden, so wird das Signal vom GAL auf HIGH-Pegel (1) gezogen. Ist der Schalter geschlossen, wird das Signal auf LOW-Pegel (0) gezogen.

Addressbereich ROM K1 K0 C1 C0 B0
f000-ffff Zeichensatz 3     1 1  
e000-f000 Zeichensatz 2     1 0  
d000-e000 Zeichensatz 1     0 1  
c000-d000 Zeichensatz 0     0 0  
a000-c000 Basic 1         1
8000-a000 Basic 0         0
6000-8000 Kernal 3 1 1      
4000-6000 Kernal 2 1 0      
2000-4000 Kernal 1 0 1      
0000-2000 Kernal 0 0 0      

Lizenz

                   reprom64 Hardware and Firmware
     Copyright (c) 2015, Henning Bekel <h.bekel@googlemail.com>

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