Doc64 #26 | Commodore C64 | What's the PLA for and how does it work?
Videobeschreibung:
Today I want to show you ...
- What is the PLA (Programmable Logic Array)?
- What is the PLA for?
- What is the PLA's job?
- How does the PLA work?
- What is inside the PLA?
- Are there replacements for the PLA?
- Measuring the signals at the PLA
- Measuring CAS, CASRAM, AEC, ROMH, ROML, VA12, VA13, VA14, KERNAL, BASIC, CHAROM, IO, BA, GR/W, R/W, EXROM, HRAM
- PLA 906114-01, MOS 906114-01, Signetic 82S100
- PLA U17
PLA alternatives:
- EPROM+adapter (best suited EPROM: STMicroelectronics M27C512-90B6)
- realPLA (by ‚skoe‘ Thomas Giesel)
www.c64-wiki.de/wiki/realPLA
- SuperPLA V4 (by Jens Schönfeld, INDIVIDUAL Computers)
icomp.de/shop-icomp/de/shop/p...
amigastore.eu/152-superpla-v4...
- PLA20V8 consists of two GAL20V8B
- PLAnkton
www.polyplay.xyz/PLAnkton-PLA...
And many more …
Have a look at c64os.com/buyersguide/
Sources:
C64 memory map:
www.c64-wiki.de/wiki/PLA_(C64...)
www.c64-wiki.com/wiki/PLA_(C6...)
C64 PLA dissected:
skoe.de/docs/c64-dissected/pla...
by Thomas ‚skoe‘ Giesel
VERSA Cart and C64 ROMs (C64 OS Homepage by Gregory Nacu):
www.c64os.com/post/versa64cart
Standard Memory Configuration C64 PLA:
William Levak and Ann Arbor, 1986, Commodore 64 Memory Configurations,
The Transactor, Volume 6, Issue 05, p. 51-55.
Picture „Standard Memory Config“:
zimmers.net/anonftp/pub/cbm/ma...
All mem configs from page p051.jpg to p057.jpg on zimmers.net:
zimmers.net/anonftp/pub/cbm/ma...
Picture „EPROM as PLA replacement“:
www.vic20.de/html/eprom_pla_82...
PLA fault screens:
www.pictorial64.com/
Sven Petersens Block Diagram
tech.guitarsite.de/c64_block_d...
Sven Petersens Osciloscope Screenshots
tech.guitarsite.de/c64_scope.h...
Helpfull links:
www.pictorial64.com/
Trouble Shooting and Repair Guides:
archive.org/details/Commodore...
archive.org/details/C64-C64C_...
My Twitter Account:
/ doktor643
Music:
- Shades, 1986, 64er Markt&Technik by Chris_Huelsbeck
Vielen Dank für das lehrreiche Video. Sofort gespeichert!
Thanks, this is very helpful to diagnose using an oscilloscope.
I still don't understand how a simple EPROM (that's just a read-only memory, a static content) can be used to replace a PLA that, according the explanation, seems to be a dynamic chip, something more similar to a bunch of 74xxx logic ports. I didn't find an explanation for that yet.
Hi! That's not so complicated. An EPROM has Adress Inputs and Data Outputs. If you access an adress then, according to the "program" in the EPPROM, it will give you something on the data output pins. That's what the PLA is doing also. Greetings, Doc64!
@@doktor6495So, in effect, you are actually programming a set of truth tables into the EPROM that will present a certain data pattern on the data pins whenever a certain combination of address lines are selected for the EPROM. When the EPROM has certain address lines selected the data output pins will be emulating the pin outputs of the original PLA which are stored internally at the address you presented on it's address bus. A very clever work around ;)
grüße, kann das sein das das der "charakterchip" ist?...ich habe einen c64 rev.4 und zeichen werden mit einem punkt (invers) dargestellt? grüße und danke für den einblick, hier lernt man was..und ne super zeit dir!
Werden alle Zeichen als Punkt (invers) dargestellt?
@@doktor6495 nein, nur der curser und manche tasten funktionieren nicht zuverlässig...habe schon 3 tastaturen versucht, es muss am bord liegen..;-)
@@KrautRockt Dann könnte es tatsächlich der CHAR-ROM sein oder der CIA1 sein. Schöne Grüße, Doktor64!
@@doktor6495 hast du nen plan, oder link..das ich mir das meinmal ansehen kann?..lg und dankeschön für deine mühe!..
@@KrautRockt Hier findest Du alle C64 Schaltpläne ... zimmers.net/anonftp/pub/cbm/schematics/computers/c64/index.html