
A very simple download cable for a chain of Lattice ISP devices:


DB25 PC parallel port		Lattice ISP port	signal
(male connector)		(8-pin header)

DI3 pin 15		...	pin 1			VCC
DI6 pin 10		...	pin 2			SDO
DO0 pin 2		...	pin 3			SDI
DO3 pin 5		...	pin 4			ISPEN (unused)
				pin 5			no connect
DO2 pin 4		...	pin 6			MODE
GND pin 20		...	pin 7			GND
DO1 pin 3		...	pin 8			SCLK

Also, pins 8 (DO6) and 12 (DI5) on the PC side must be connected together.

There's no need of buffers if you keep the cable short (about 30cm).

Recommended procedure:
- generate the .isp binary file to be downloaded (see makefile)
- turn the PC off and connect the cable between the PC parallel port
  and the DTC3 card. Pin 1 of the ISP port (VCC) is on the side of the
  two C012 sockets and BDM connector JP4, pin 8 on the side of the PC
  card mounting bracket and power connector JP2.
- turn the PC on, download the data into the ISP chain with turbo.exe
- turn the PC power off and on again.

