Occasional Contributorprogramming successful but no function of CPLD
Hi, I am quite new with CPLD design and hope to get help here.
For test purposes and learning I made a simple schematic with an external clock of 1 kHz, a 4bit counter (74161) and a BCD to 7 segment decoder (7448). All 4 outputs from counter and 7 outputs from decoder are available on pins of the CPLD.
I programmed a MAX300 EPM3064ATC44 on a self made board with a USB Blaster Rev. c. Quartus II programmer reported 100% successful programming and verification. But the counter outputs don't look like binary counting. They are totally confused.
I also programmed the same schematic to a MAXII EPM240T100 on a test board from ebay. Again programming was successful but counter outputs are confused.
The USB Blaster is a clone from ebay. It contains a STM32FEB but no output driver for level conversion. Both boards, my self made one and the board from ebay, are powered with 3.3 V and also VCC_IO for both chips is 3.3 V. Therefore level conversion is not necessary.
The board from ebay was delivered programmed with a blinking example. Therefore the chip should be ok.
What could have happened that after successful programming the chips don't work as expected?
A picture of the ebay board and USB Blaster ist attached.
Hi,
which series resistor value? Clock edge may be too slow and cause multiple transitions. As you say it's a self designed board, insufficient power supply bypassing and ground bounce can cause irregular CPLD behaviour.
