R
Spartan and Spartan-XL Families Field Programmable Gate Arrays
•
The 16 x 1 single-port configuration contains a RAM
array with 16 locations, each one-bit wide. One 4-bit
address decoder determines the RAM location for write
and read operations. There is one input for writing data
and one output for reading data, all at the selected
address.
Table 9: Single-Port RAM Signals
RAM Signal
D0 or D1
A[3:0]
Function
Data In
CLB Signal
DIN or H1
Address
Address
Write Enable
Clock
F[4:1] or G[4:1]
A4 (32 x 1 only)
WE
H1
SR
K
•
The (16 x 1) x 2 single-port configuration combines two
16 x 1 single-port configurations (each according to the
preceding description). There is one data input, one
data output and one address decoder for each array.
These arrays can be addressed independently.
WCLK
SPO
Single Port Out
(Data Out)
F
or G
OUT OUT
•
•
The 32 x 1 single-port configuration contains a RAM
array with 32 locations, each one-bit wide. There is one
data input, one data output, and one 5-bit address
decoder.
n
The dual-port mode 16 x 1 configuration contains a
RAM array with 16 locations, each one-bit wide. There
are two 4-bit address decoders, one for each port. One
port consists of an input for writing and an output for
reading, all at a selected address. The other port
consists of one output for reading from an
16 x 1
32 x 1
RAM ARRAY
n
A[n-1:0]
independently selected address.
WE
WRITE
CONTROL
READ
OUT
The appropriate choice of RAM configuration mode for a
given design should be based on timing and resource
requirements, desired functionality, and the simplicity of the
design process. Selection criteria include the following:
Whereas the 32 x 1 single-port, the (16 x 1) x 2 single-port,
and the 16 x 1 dual-port configurations each use one entire
CLB, the 16 x 1 single-port configuration uses only one half
of a CLB. Due to its simultaneous read/write capability, the
dual-port RAM can transfer twice as much data as the sin-
gle-port RAM, which permits only one data operation at any
given time.
SPO
D0 or D1
WCLK
DS060_12_043010
Notes:
1. The (16 x 1) x 2 configuration combines two 16 x 1 single-port
RAMs, each with its own independent address bus and data
input. The same WE and WCLK signals are connected to both
RAMs.
2. n = 4 for the 16 x 1 and (16 x 1) x 2 configurations. n = 5 for the
32 x 1 configuration.
Figure 12: Logic Diagram for the Single-Port RAM
CLB memory configuration options are selected by using
the appropriate library symbol in the design entry.
Writing data to the single-port RAM is essentially the same
as writing to a data register. It is an edge-triggered (syn-
chronous) operation performed by applying an address to
the A inputs and data to the D input during the active edge
of WCLK while WE is High.
Single-Port Mode
There are three CLB memory configurations for the sin-
gle-port RAM: 16 x 1, (16 x 1) x 2, and 32 x 1, the functional
organization of which is shown in Figure 12.
The timing relationships are shown in Figure 13. The High
logic level on WE enables the input data register for writing.
The active edge of WCLK latches the address, input data,
and WE signals. Then, an internal write pulse is generated
that loads the data into the memory cell.
The single-port RAM signals and the CLB signals (Figure 2,
page 4) from which they are originally derived are shown in
Table 9.
14
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DS060 (v1.6) September 19, 2001
Product Specification
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