
30 www.xilinx.com 7 Series FPGAs Memory Resources
UG473 (v1.11) November 12, 2014
Chapter 1: Block RAM Resources
Inverting Control Pins
For each port, the eight control pins (CLK, EN, RSTREG, and RSTRAM) each have an
individual inversion option. EN, RSTREG, and RSTRAM control signals can be configured
as active-High or -Low, and the clock can be active on a rising or falling edge (active-High
on rising edge by default), without requiring other logic resources.
GSR
The global set/reset (GSR) signal of a 7 series device is an asynchronous global signal that
is active at the end of device configuration. The GSR can also restore the initial
7 series device state at any time. The GSR signal initializes the output latches to the INIT
(simple dual port), or to the INIT_A and INIT_B value (true dual port). See Block RAM
Attributes. A GSR signal has no impact on internal memory contents. Because it is a global
signal, the GSR has no input pin at the functional level (block RAM primitive). While GSR
is asserted, a write operation is not always successful.
Unused Inputs
Unused data inputs should be connected Low. Unused address inputs should be
connected High.
Block RAM Address Mapping
Each port accesses the same set of 18,432 or 36,864 memory cells using an addressing
scheme dependent on whether it is a RAMB18E1 or RAMB36E1. The physical RAM
locations addressed for a particular width are determined using these formulae (of interest
only when the two ports use different aspect ratios):
END=((ADDR+1)
× Width) -1
START = ADDR
× Width
Table 1-14 shows low-order address mapping for each port width.
Table 1-14: Port Address Mapping
Port
Width
Parity
Locations
Data Locations
1 N.A. 313029282726252423222120191817161514131211109876543210
2 1514131211109876543210
4 76543210
8 + 1 321 0 3 2 1 0
16 + 2 1 0 1 0
32 + 4 0 0
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