Answers Database

Configuration: APM - Can RDY/BSY be used to signal start of configuration instead of INIT?


Record #2026

Product Family:  Hardware

Product Line:  4000

Problem Title:
Configuration: APM - Can RDY/BSY be used to signal start of
configuration instead of INIT?



Problem Description:
Keywords: config, async, periph, rdy, bsy

Urgency: Standard

General Description:

Can the RDY/BSY signal be used to indicate when asynchronous peripheral mode
configuration can commence instead of using the INIT pin?


Solution 1:

The RDY/BSY pin may be used to indicate when the FPGA can accept configuration d
ata in asynchronous peripheral mode.  However, a pulldown
should be used to keep this pin at a logic low during power-up.

After Vcc has been applied to the FPGA, but before the mode pins have been
sampled, all I/Os, including the RDY/BSY pin, will be high-impedence and
pulled high.  After the mode pins have been sampled, if APM has been
selected, then the RDY/BSY pin will be driven low during a memory clearing
cycle.	When the FPGA is ready to accept configuration data the RDY/BSY pin
will be driven HIGH.  Adding a 2.2~3.3K ohm resistor to this pin will hold it
LOW until the FPGA can accept data.



End of Record #2026