XC3S400-4FT256C Xilinx Inc, XC3S400-4FT256C Datasheet - Page 52

• Manufacturer Part Number: XC3S400-4FT256C
• Description: SEMI CONDUCTOR
• Manufacturer: Xilinx Inc

Specifications of XC3S400-4FT256C

• Case: BGA
• Dc: 04+

Spartan-3 FPGA Family: Functional Description
Configuration is automatically initiated after power-on
unless it is delayed by the user. INIT_B is an open-drain line
that the FPGA holds Low during the clearing of the configu-
ration memory. Extending the time that the pin is Low
causes the configuration sequencer to wait. Thus, configu-
ration is delayed by preventing entry into the phase where
data is loaded.
The configuration process can also be initiated by asserting
the PROG_B pin. The end of the memory-clearing phase is
signaled by the INIT_B pin going High. At this point, the
configuration data is written to the FPGA. The FPGA pulses
the Global Set/Reset (GSR) signal at the end of configura-
tion, resetting all flip-flops. The completion of the entire pro-
cess is signaled by the DONE pin going High.
The default start-up sequence, shown in
as a transition to the User mode. The default start-up
sequence is that one CCLK cycle after DONE goes High,
the Global Three-State signal (GTS) is released. This per-
mits device outputs to which signals have been assigned to
52
54
Start-Up Clock
Start-Up Clock
Notes:
1.
Figure 29: Default Start-Up Sequence
The BitGen option StartupClk in the Xilinx
development software selects the CCLK input,
TCK input, or a user-designated clock input (via
the STARTUP_SPARTAN3 primitive) for receiving
the clock signal that synchronizes Start-Up.
DONE
DONE
Phase
Phase
GWE
GWE
GTS
GTS
DONE High
0
0
1
1
Default Cycles
Sync-to-DONE
2
2
3
3
4
4
5
5
Figure
DS099_028_060905
6 7
6 7
29, serves
www.xilinx.com
become active. One CCLK cycle later, the Global Write
Enable (GWE) signal is released. This permits the internal
storage elements to begin changing state in response to the
design logic and the user clock.
The relative timing of configuration events can be changed
via the BitGen options in the Xilinx development software. In
addition, the GTS and GWE events can be made dependent
on the DONE pins of multiple devices all going High, forcing
the devices to start synchronously. The sequence can also
be paused at any stage, until lock has been achieved on
any DCM.
Readback
Using Slave Parallel mode, configuration data from the
FPGA can be read back. Readback is supported only in the
Slave Parallel and Boundary-Scan modes.
Along with the configuration data, it is possible to read back
the contents of all registers, distributed RAM, and block
RAM resources. This capability is used for real-time debug-
ging.
Additional Configuration Details
Additional details about the Spartan-3 FPGA configuration
architecture and command set are available in the “Spar-
tan-3 Generation Configuration User Guide” (UG332) and
the "Spartan-3 Advanced Configuration Architecture" appli-
cation note (
Powering Spartan-3 FPGAs
Voltage Regulators
Various power supply manufacturers offer complete power
solutions for Xilinx FPGAs, including some with integrated
multi-rail regulators specifically designed for Spartan-3
FPGAs. The
vendor solution guides as well as Xilinx power estimation
and analysis tools.
Power Distribution System (PDS) Design and
Bypass/Decoupling Capacitors
Good power distribution system (PDS) design is important
for all FPGA designs, especially for high-performance appli-
cations. Proper design results in better overall performance,
lower clock and DCM jitter, and a generally more robust
system. Before designing the printed circuit board (PCB) for
the FPGA design, review "Power Distribution System (PDS)
Design: Using Bypass/Decoupling Capacitors" (
Power-On Behavior
Spartan-3 FPGAs have a built-in Power-On Reset (POR)
circuit that monitors the three power rails required to suc-
cessfully configure the FPGA. At power-up, the POR circuit
holds the FPGA in a reset state until the V
and V
CCO
Bank 4 supplies reach their respective input
XAPP452
Xilinx Power Corner
).
DS099-2 (v2.2) May 25, 2007
website provides links to
Product Specification
CCINT
XAPP623
, V
CCAUX
).
R
,