Spartan-3E FPGA Family: Functional Description
DS312 (v4.1) July 19, 2013
Product Specification
39
Table 23: Block RAM Port Signals
Signal
Description
Port A
Signal
Name
Port B
Signal
Name
Direction
Function
Address Bus
ADDRA
ADDRB
Input
The Address Bus selects a memory location for read or write operations.
The width (w) of the port’s associated data path determines the number of
available address lines (r), as per
Table 22.Whenever a port is enabled (ENA or ENB = High), address transitions must
meet the data sheet setup and hold times with respect to the port clock
be met even if the RAM read output is of no interest.
Data Input Bus
DIA
DIB
Input
Data at the DI input bus is written to the RAM location specified by the
address input bus (ADDR) during the active edge of the CLK input, when
the clock enable (EN) and write enable (WE) inputs are active.
It is possible to configure a port’s DI input bus width (w-p) based on
Table 22. This selection applies to both the DI and DO paths of a given port.
Parity Data Input(s)
DIPA
DIPB
Input
Parity inputs represent additional bits included in the data input path.
Although referred to herein as “parity” bits, the parity inputs and outputs
have no special functionality for generating or checking parity and can be
used as additional data bits. The number of parity bits ‘p’ included in the DI
(same as for the DO bus) depends on a port’s total data path width (w). See
Data Output Bus
DOA
DOB
Output
Data is written to the DO output bus from the RAM location specified by the
address input bus, ADDR. See the DI signal description for DO port width
configurations.
Basic data access occurs on the active edge of the CLK when WE is
inactive and EN is active. The DO outputs mirror the data stored in the
address ADDR memory location. Data access with WE active if the
accesses data after the write takes place.
READ_FIRST accesses data
before the write occurs. A third attribute,
NO_CHANGE, latches the DO
details on the WRITE_MODE attribute.
Parity Data
Output(s)
DOPA
DOPB
Output
Parity outputs represent additional bits included in the data input path. The
number of parity bits ‘p’ included in the DI bus (same as for the DO bus)
depends on a port’s total data path width (w). See the DIP signal
description for configuration details.
Write Enable
WEA
WEB
Input
When asserted together with EN, this input enables the writing of data to
the RAM. When WE is inactive with EN asserted, read operations are still
possible. In this case, a latch passes data from the addressed memory
location to the DO outputs.
Clock Enable
ENA
ENB
Input
When asserted, this input enables the CLK signal to perform read and write
operations to the block RAM. When inactive, the block RAM does not
perform any read or write operations.
Set/Reset
SSRA
SSRB
Input
When asserted, this pin forces the DO output latch to the value of the
SRVAL attribute. It is synchronized to the CLK signal.
Clock
CLKA
CLKB
Input
This input accepts the clock signal to which read and write operations are
synchronized. All associated port inputs are required to meet setup times
with respect to the clock signal’s active edge. The data output bus responds
after a clock-to-out delay referenced to the clock signal’s active edge.