Sundance SMT351T User Manual
Page 12
SMT351T User Guide
Page 12 of 37
Last Edited: 04/09/2009 11:26:00
• If your FPGA design does not implement comport3,
o
do not use the Reset signal generated by the CPLD but use the TIM reset signal
as your design’s reset. You can use JTAG to configure your FPGA with your
application and the design will reset and run everytime you issue a new TIM
reset.
• If your design implements comport3
o
Set the switch to configure the FPGA from flash after reset. In this way a default
bitstream being stored in flash will be loaded in the FPGA by the CPLD.
In this manner the CPLD has gone trhough the cycle of configuring the
FPGA and releases the reset (FPGAresetn)
Then you can reconfigure the FPGA via JTAG with your application.
o
Set the switch to configure from comport 3. After reset, configure the FPGA via
JTAG and provide an end key word on comport 3 to the CPLD so that it releases
the Reset. (FPGAresetn).
4.2.6 FPGA Reset Scheme
The CPLD is connected to a TIM global Reset signal provided to the SMT351T via its primary
TIM connector pin 30. (See
23H23HH
TI TIM specification & User’s guide
H
).
This signal goes to the CPLD and the FPGA.
Nevertheless as a general rule for good practice, the FPGA should not use this reset but should
use the reset signal generated by the CPLD.
The CPLD provides another signal called FPGAResetn that offers a better Reset control over
the FPGA.
At power up or on reception of a low TIM global Reset pulse, the CPLD drives the
FPGAResetn signal low and keeps it low.
This is used to keep the FPGA design in reset.
A new FPGA configuration bitstream can then be downloaded.
When the ENDKEY has been received, the CPLD drives FPGAResetn high.
Use FPGAResetn for the Global Reset signal of your FPGA
designs.
In this manner, you can control your FPGA design Reset activity and you will also avoid
possible conflicts on ComPort 3 if your FPGA design implements it.
(Comport3 is a communication resource shared by the CPLD and the FPGA. But only 1 entity
is allowed to use it at a time).