Description
When configuration is complete on an ACEX® or FLEX® device, the device releases the CONF_DONE pin. From there, a pull-up resistor takes the DCLK signal to the logic-high level.
If the pull-up resistor is far away from the device, the rise time of the CONF_DONE pin may be too slow and the DCLK signal will be unable to latch the high state of the CONF_DONE pin.
This will cause the device to require more than 20 DCLK cycles to complete initialization.
There are two possible solutions to this problem:
- Use the smallest possible resistor as a pull-up for the CONF_DONE pin (around 500
).
- Move the pull-up resistor closer to the device to decrease the rise time of the CONF_DONE pin.