Minimig Board v1.0 schematic

Board schematic for Minimig board v1.0

Audio output via 3,5mm jack

Voltage level: (3.3V/(560ohm + 560ohm + 32ohm))*32 ohm*1000 = 91,7mV
Back EMF issues?
Head phones

4 bit resistor ladder D/A

Notice the resistor of 560 ohm. May cause inlinear output.

FPGA Xilinx XC3S400-4PQ208C

FPGA core power +1,25V +2,5V using LM1117MP-ADJ

FPGA decoupling

Joystick 0

Joystick 1

Jtag

Program & Menu button, 31/15kHz selection, Power & Disc led

Keyboard & Mouse connections

MC68000

MC68000 Decoupling

Generation of 4.433619 MHz PAL video MCLK using 74HC4060 (NTSC=3.579545MHz)

PATCH needed to get rev 1 board working:

Disconnect net SPI_DOUT from pin 81 of FPGA.

Connect net SPI_DOUT to pin 19 of FPGA (net USER3).

REASON:

Pin 81 is an output during FPGA config that blocks SPI to MMC during startup.

MCU PIC18LF252I/SP

Asynchronous static ram 512 x 16 bit (2 chips)

Serial RS232 using MAX232

SD Card slot

Spare I/O directly connected to FPGA