OR3C80 datasheet(99/210 Pages) AGERE

99 / 210 page

Lucent Technologies Inc.

Data Sheet

June 1999

ORCA Series 3C and 3T FPGAs

FPGA Configuration Modes (continued)

Daisy-Chaining with Boundary Scan

Multiple FPGAs can be configured through the JTAG ports by using a daisy-chain of the FPGAs. This daisy-chain-

ing operation is available upon initial configuration after powerup, after a power-on reset, after pulling the program

pin to reset the chip, or during a reconfiguration if the EN_JTAG RAM has been set.

All daisy-chained FPGAs are connected in series. Each FPGA reads and shifts the preamble and length count in

on the positive TCK and out on the negative TCK edges.

An upstream FPGA that has received the preamble and length count outputs a high on TDO until it has received

the appropriate number of data frames so that downstream FPGAs do not receive frame start bit pairs. After load-

ing and retransmitting the preamble and length count to a daisy-chain of downstream devices, the lead device

loads its configuration data frames.

The loading of configuration data continues after the lead device had received its configuration read into TDI of

downstream devices on the positive edge of TCK, and shifted out TDO on the negative edge of TCK. Figure 63

shows the connections for loading multiple FPGAs in a JTAG daisy-chain configuration.

OR3C80 Datasheet(PDF) 99 Page - Agere Systems