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AR# 7478

4.1i XC4000E MAP - MAP cannot combine dual-port RAM with registers into the same CLB when a local set/reset signal is used.

Description

Keywords: RAM, register, CLB, combine, dual-port, dual port

Urgency: Standard

General Description:
When distributed RAM is used to generate a dual-port RAM, if the output data signal is registered to enable synchronous reads from the RAM, MAP will not push the register into the same CLB.

Solution

If the register is using a local control signal such as CLR, MAP will be unable to combine the two into one CLB. This is because the CLR signal is brought into the CLB using one of the control signals (SR) that has already been used as the write enable in the dual-port RAM.
AR# 7478
Date Created 09/09/1999
Last Updated 06/13/2002
Status Archive
Type General Article