251715-01 / 252535-01 memory controller (C64C) pinout

DIP-64. PLA, DRAM address multiplexer and chip selects in one chip (C64C short board)

Replaces the 82S100 PLA and its helpers on the 250469 short board. It makes the ROM, I/O and cartridge selects, the chip selects for the VIC-II, SID and both CIAs, and the multiplexed DRAM address MA0-MA7 with gated /CAS. Rev A boards fit the 251715-01 with a separate 2114 color RAM at U19 (pin 17 /COLRAM selects it). Rev B boards fit the 252535-01, which holds the color RAM itself: pins 18-21 carry its four data bits, and pin 17 has no RAM to select. Do not swap one type for the other without checking the board. The package is a shrink DIP: 64 pins in about the length of the 40-pin VIC-II (1.78 mm pitch on the board photos). A dead one gives a black screen, as a dead PLA does.

Open the interactive 251715 pinout

Pins

PinNameTypeSignal
1A13addrAddress bit 13.
2A14addrAddress bit 14.
3A15addrAddress bit 15.
4R/WctrlRead/write from the CPU. HIGH = read, LOW = write.
5LORAMctrlCPU port bit 0: BASIC ROM banking.
6HIRAMctrlCPU port bit 1: KERNAL ROM banking.
7CHARENctrlCPU port bit 2: character ROM or I/O at $D000.
8NMIctrlNMI line to the CPU (schematic name NMI). Pin 9 takes the RESTORE key. UNVERIFIED
9RESTOREctrlRESTORE key input. UNVERIFIED
10/VA14ctrlVIC-II bank select bit 14, from CIA2 port A.
11/VA15ctrlVIC-II bank select bit 15, from CIA2 port A.
12/CIA2ctrlCIA2 chip select ($DD00-$DDFF).
13/CHAROMctrlCharacter ROM select (U5).
14/BASICctrlBASIC ROM select. Drawn on the rev A schematic; the rev B schematic draws a wire only at pin 15 for the one BASIC/KERNAL ROM. UNVERIFIED
15/KERNALctrlKERNAL ROM select (labeled /BASIC and /KERNAL on the rev B schematic).
16VSSground0 V.
17/COLRAMctrl251715: color RAM select to the 2114 at U19 (pin 8). 252535: no external color RAM; the rev B schematic draws this pin to +5 V. UNVERIFIED
18CAS0 / D1data251715: CAS0, not connected on the board. 252535: color RAM data bit D1, on the VIC-II color data lines D8-D11. UNVERIFIED
19CAS1 / D2data251715: CAS1, not connected on the board. 252535: color RAM data bit D2. UNVERIFIED
20CAS2 / D3data251715: CAS2, not connected on the board. 252535: color RAM data bit D3. UNVERIFIED
21CAS3 / D4data251715: CAS3, not connected on the board. 252535: color RAM data bit D4. UNVERIFIED
22/CASRAMctrlGated /CAS to the DRAMs (through R101).
23RAM R/WctrlWrite enable to the DRAMs (/WE).
24MA6addrMultiplexed DRAM address bit 6.
25MA3addrMultiplexed DRAM address bit 3.
26MA0addrMultiplexed DRAM address bit 0.
27MA2addrMultiplexed DRAM address bit 2.
28MA4addrMultiplexed DRAM address bit 4.
29MA1addrMultiplexed DRAM address bit 1.
30MA5addrMultiplexed DRAM address bit 5.
31MA7addrMultiplexed DRAM address bit 7.
32NCncNo connection.
33VSSground0 V.
34/CIA1ctrlCIA1 chip select ($DC00-$DCFF).
35/CASctrlColumn address strobe from the VIC-II.
36/RASctrlRow address strobe from the VIC-II.
37Φ0clockSystem clock Φ0 from the VIC-II.
38AECctrlAddress Enable Control from the VIC-II.
39BActrlBus Available from the VIC-II.
40/VICctrlVIC-II chip select ($D000-$D3FF).
41VA6addrVIC-II address bit 6 (for the DRAM address multiplexer).
42VA7addrVIC-II address bit 7.
43/SIDctrlSID chip select ($D400-$D7FF).
44/ROMLctrlCartridge low ROM select (expansion port).
45/IO2ctrlI/O 2 select ($DF00-$DFFF, expansion port).
46/EXROMctrlEXROM line from the expansion port.
47/GAMEctrlGAME line from the expansion port.
48VSSground0 V.
49/IO1ctrlI/O 1 select ($DE00-$DEFF, expansion port).
50/ROMHctrlCartridge high ROM select (expansion port).
51A0addrAddress bit 0.
52A1addrAddress bit 1.
53A2addrAddress bit 2.
54A3addrAddress bit 3.
55A4addrAddress bit 4.
56A5addrAddress bit 5.
57A6addrAddress bit 6.
58A7addrAddress bit 7.
59A8addrAddress bit 8.
60A9addrAddress bit 9.
61A10addrAddress bit 10.
62A11addrAddress bit 11.
63A12addrAddress bit 12.
64VDDpower+5 V supply.

Fitted in

Sources