DS001 Datasheet, PDF (36/99 Pages) Xilinx, Inc – Spartan-II FPGA Family

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Spartan-II FPGA Family: Functional Description
At the third rising edge of CLKA, the T_BCCS parameter is
violated with two writes to memory location 0x0F. The DOA
and DOB busses reflect the contents of the DIA and DIB
busses, but the stored value at 0x7E is invalid.
At the fourth rising edge of CLKA, a read operation is
performed at memory location 0x0F and invalid data is
present on the DOA bus. Port B also executes a read
operation to memory location 0x0F and also reads invalid
data.
At the fifth rising edge of CLKA a read operation is
performed that does not violate the T_BCCS parameter to the
previous write of 0x7E by Port B. THe DOA bus reflects the
recently written value by Port B.
Initialization
The block RAM memory can initialize during the device
configuration sequence. The 16 initialization properties of
64 hex values each (a total of 4096 bits) set the initialization
of each RAM. These properties appear in Table 14. Any
initialization properties not explicitly set configure as zeros.
Partial initialization strings pad with zeros. Initialization
strings greater than 64 hex values generate an error. The
RAMs can be simulated with the initialization values using
generics in VHDL simulators and parameters in Verilog
simulators.
Initialization in VHDL
The block RAM structures may be initialized in VHDL for
both simulation and synthesis for inclusion in the EDIF
output file. The simulation of the VHDL code uses a generic
to pass the initialization.
Initialization in Verilog
The block RAM structures may be initialized in Verilog for
both simulation and synthesis for inclusion in the EDIF
output file. The simulation of the Verilog code uses a
defparam to pass the initialization.
Block Memory Generation
The CORE Generator™ software generates memory
structures using the block RAM features. This program
outputs VHDL or Verilog simulation code templates and an
EDIF file for inclusion in a design.
Table 14: RAM Initialization Properties
Property
Memory Cells
INIT_00
255 to 0
INIT_01
511 to 256
INIT_02
767 to 512
INIT_03
1023 to 768
INIT_04
1279 to 1024
Table 14: RAM Initialization Properties
Property
Memory Cells
INIT_05
1535 to 1280
INIT_06
1791 to 1536
INIT_07
2047 to 1792
INIT_08
2303 to 2048
INIT_09
2559 to 2304
INIT_0a
2815 to 2560
INIT_0b
3071 to 2816
INIT_0c
3327 to 3072
INIT_0d
3583 to 3328
INIT_0e
3839 to 3584
INIT_0f
4095 to 3840
For design examples and more information on using the
Block RAM, see XAPP173, Using Block SelectRAM+
Memory in Spartan-II FPGAs.
Using Versatile I/O
The Spartan-II FPGA family includes a highly configurable,
high-performance I/O resource called Versatile I/O to
provide support for a wide variety of I/O standards. The
Versatile I/O resource is a robust set of features including
programmable control of output drive strength, slew rate,
and input delay and hold time. Taking advantage of the
flexibility and Versatile I/O features and the design
considerations described in this document can improve and
simplify system level design.
Introduction
As FPGAs continue to grow in size and capacity, the larger
and more complex systems designed for them demand an
increased variety of I/O standards. Furthermore, as system
clock speeds continue to increase, the need for
high-performance I/O becomes more important. While
chip-to-chip delays have an increasingly substantial impact
on overall system speed, the task of achieving the desired
system performance becomes more difficult with the
proliferation of low-voltage I/O standards. Versatile I/O, the
revolutionary input/output resources of Spartan-II devices,
has resolved this potential problem by providing a highly
configurable, high-performance alternative to the I/O
resources of more conventional programmable devices.
The Spartan-II FPGA Versatile I/O features combine the
flexibility and time-to-market advantages of programmable
logic with the high performance previously available only
with ASICs and custom ICs.
Each Versatile I/O block can support up to 16 I/O standards.
Supporting such a variety of I/O standards allows the
DS001-2 (v2.8) June 13, 2008
Product Specification
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