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AR# 23152

8.1i EDK - "WARNING:Timing:3238 - Timing Constraint... This violates the minimum period..."

Description

When implementing my PPC system, I receive the following warnings:

WARNING:Timing:3238 - Timing Constraint

"TS_inst_ppc_system_dcm_ppc_dcm_ppc_CLK2X_BUF = PERIOD TIMEGRP

"inst_ppc_system_dcm_ppc_dcm_ppc_CLK2X_BUF"

TS_inst_ppc_system_dcm_bus_dcm_bus_CLKFX_BUF / 2 HIGH 50%;"

fails the pulse width check for clock inst_ppc_system/ppc_clk because the low value (1333 ps) or high value (1333

ps) is less than the minimum internal pulse width limits of 2000 ps low and 2000 ps high. Please increase the period

of the constraint to remove this timing failure.

WARNING:Timing:3232 - Timing Constraint

"TS_inst_ppc_system_dcm_ppc_dcm_ppc_CLK2X_BUF = PERIOD TIMEGRP

"inst_ppc_system_dcm_ppc_dcm_ppc_CLK2X_BUF"

TS_inst_ppc_system_dcm_bus_dcm_bus_CLKFX_BUF / 2 HIGH 50%;"

fails the minimum period check for clock inst_ppc_system/ppc_clk because the period constraint value (2666 ps) is

less than the minimum internal period limit of 4000 ps. Please increase the period of the constraint to remove this

timing failure.

According to this warning, the maximum frequency of PPC is 250 MHz. But according to the data sheet for -11 (xc4vfx60 -11 672 used in above test), the PPC frequency is 400 MHz.

Solution

This warning can be safely ignored. This will be fixed in ISE 8.2i.

AR# 23152
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article