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Commodore 264 Diag and development

2 years ago 1563
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DIAG264 circuitboard, with extra header and pal/ntsc option.


Schematic Card and Userport




ID Value Qty. Package Components
1 CONN_01X25 2 1X25 J3,J2
2 HDR2X25_numbered_by_row 1 C264 EXPANSION CARD SLOT P1
3 27C256AG 1 DIP28-600 U1
4 Header-Male-2.54_1x3 2 HDR-3X1/2.54 P2,P3
5 UserPort 1 USER PORT P5
6 74HCT244N 1 DIP-20 U2
7 Header-Male-2.54_1x8 2 HDR-8X1/2.54 JOY1,JOY2
8 110 8 AXIAL-0.3 R1,R2,R3,R4,R5,R6,R7,R8
9 2.54mm 1*20P Female header 1 HDR-20X1/2.54 P4_C16
10 1N4148 8 DIODE_DO35 D1,D2,D3,D4,D5,D6,D7,D8
11 2.54mm 1*20P Female header 1 C116/PLUS4 KEYBOARD CARD EDGE P4_P4/C116
12 1k 8 AXIAL-0.3 R12,R15,R11,R16,R9,R10,R14,R13
13 36ce4bc8a968ff7266824a85f89dcb5b 1 KEY-6.0*6.0-2 KEY1




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Comments (5)

Sándor Vass Reply

first thanks for these PCB designs, helped me a lot. Actually I converted them to a 28C256 based solution and my cart is working as expected!

I'm not sure but I think I've found two problems in the schematics.
1) On the tab 264 (the one where the joy sensor is separated from cart), the D8 is reversed on the keyboard sensor PCB.
2) header on-off is reversed also. The cart is not working when ON, and starts up, when OFF. (/CE must be held low for ON, not on VCC)
3) the small drills that separate the PCB areas are actually vias, so they have metal inside. This might cause problems later..

My problem is that I produced the other scenario (when joy sensing is on the CART) and the keyboard sensing doesn't work either, though the keyboard of the C16 is fully functional and the schematics of that board is fine...

Sándor Vass Reply

one more thing: 1k resistors are too high values on the keyboard sensing PCB. Use 110 ohms for R9-R16 also and the module will work properly.

jeroen1328 Reply


Thank you for your comments.
I will check your remarks.


Jeroen Vlasveld

Sándor Vass Reply

one more thing. On the userport PCB (on both plans) the N pad is connected to the K and 7 pads. N is on GND inside the plus4, so this one makes false positive on the DIAG 264 cart program. In the schematics it is planned correctly, but on the PCB these are not correct.
Please fix this too.

jeroen1328 Reply

@vass.sanyi Issue on pin N should be fixed now.

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