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Question & Answer
Classification:
Date: Jun 12, 2001
XS40-005XL serial EEPROM and oscillator programming gremlins
Q:
I have an XS40-005XL which has been working fine for several weeks. I'm using it to help prototype and program the configuration EEPROM for a custom board that has a 4005XL. To maintain consistency between the 2 boards I reprogrammed the XS40 oscillator to 10 MHz (divisor of 10) some time ago, with no problems, nor have I had any problems programming EEPROMS (the Atmel 17C256) on the XS40 and using them in the custom board. Since yesterday I've noticed some odd behavior:
I can't program the configuration EEPROMS anymore. GXSLOAD goes through the motions and tells me the PROM is programmed, but when I run it on my own board, it's clear the program hasn't changed. I continue to follow the instructions for jumper setting provided by GXSLOAD as always.
A:
The eeprom socket on the XS40 Board is not really intended for use as an eeprom programming socket. I'm not sure how many times you have inserted/removed eeproms into the socket, but are you sure you are still getting good connectivity to the eeprom pins?
Q:
I can't run the XS40 from the EEPROM anymore. I configure the jumpers as I always have (according to the manual) but nothing happens when I power up the board. This is using a PROM that works fine on the custom board and which has the same configuration that works fine when downloaded directly to the XS40.
A:
This also points to a problem with the eeprom socket. It could also be one of the FPGA mode pins (M0, M1, M2) is in the wrong state so the FPGA isn't entering the master-serial config. mode. This might indicate a problem with the parallel port data pins not driving the mode pins to the correct values.
Q:
I can't reprogram the oscillator on the XS40. GXSSETCLK claims it has reprogrammed the clock, but I can see on a scope and through the execution of a downloaded configuration that it hasn't changed from 10 MHz.
A:
When programming the clock, the board should power up and pin 1 of the DS1075 clock chip should be at ground. This indicates it is ready to accept programming data. Then you should see a short burst of programming pulses when you run GXSSETCLK. You might check this with your scope to make sure it is happening. If you don't see the programming pulses, then this would indicate a problem with the parallel port data pins.
Once the DS1075 is reprogrammed and you return the jumper to its normal position, you should see the clock on pin 1 of the DS1075 (and pin 13 of the FPGA).
Q:
GXSTEST downloads and runs but doesn't terminate. Does it assume a 100 MHz clock, or doesn't it care?
A:
When you say "doesn't terminate", do you means that the LEDs on the XS40 Board continually flash or that the PC never indicates whether the board passed or failed?
Q:
As mentioned in 2, I can still download configurations directly to the board and they work fine. I've been using a 12V supply, with no problems until now.
A:
That shouldn't cause a problem as long as your current is not too high. The regulators will regulate this down to 5V and 3.3V.