SWTP GT-6144 Interface Schematic

This information is taken from the schematic for the hook up of the Apple1 to the SWTP GT-6144 graphics board, refer to it while reading this, especially on the PIA pins , 23, 34, 35, 37 and 38.

The chip on the left is for the PIA for the graphic board. All pins marked with a * are connected to the corresponding pin on the keyboard PIA, pins 1, 20, 21, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36. This is listed at the bottom of the sheet on the left side. Pin 22 goes to the address line A3.

The capacitor on the 74123, between pins 6 and 7. On the bottom of the sheet on the right hand side says, ì you may have to play with this capacitor a little. The capacitor governs the length of time that must elapse between each output of data to the GT-6144.

The 12 pin molex connector on the GT-6144 board is shown on the right side of the sheet.

The information right below the 12 pin molex connector has the 6820-6520 PIA pins.

1  = VSS          11 = PB1          21 = R/W         31 = D2<br />
2  = PA0          12 = PB2          22 = CS1         32 = D1<br />
3  = PA1          13 = PB3          23 = CS3*        33 = D0<br />
4  = PA2          14 = PB4          24 = CS2         34 = RESET*<br />
5  = PA3          15 = PB5          25 = ENABLE      35 = RS1*<br />
6  = PA4          16 = PB6          26 = D7          36 = RS0<br />
7  = PA5          17 = PB7          27 = D6          37 = IRQB*<br />
8  = PA6          18 = CB1          28 = D5          38 = IRQA*<br />
9  = PA7          19 = CB2          29 = D4          39 = CA2<br />
10 = PB0          20 = VCC          30 = D3          40 = CA1



Click to enlarge: Apple I - GT-6144 Interface Schematic