I want to make a simple programmer for EPM240 (to be placed in a ZIF socket), use USB Blaster and program it from Quartus. What am I to do with the I/O pins during programming since they are not connected anywhere? Leave them floating?
The EPM240(MAX II) devices only support JTAG protocol for programming the device which is In-System Programming (ISP). You can only use the Quartus programmer with the USB Blaster cable to program the MAX II device via the JTAG pins only. By default, all MAX II I/O pins are tri-stated during in-system programming. The MAX II device provides a weak pull-up resistor during ISP.
You can leave the I/O floating. Providing you've powered all the power pins it is perfectly possible to program the device in your 'simple programmer' via JTAG. You can quite easily use third party JTAG hardware/software to program these devices as well, common practice in JTAG capable CEMs.
Thank you all. I couldn't find this info in any documentation. Apparently the common thing is to program the devices in situ but that doesn't work in miniature products where there is no room for the JTAG 8-pin header.