Short Description: There is a problem with ABEL software with the implementation of an initial state for xc3k flip-flops. The software should implement a preset flip-flop as an FDC with an inverter on the D input and on the Q output. Instead it is being implemented like an xc4k preset Initial state flip-flop.
1. Using the initial state command puts an INIT property on an FD. 2. Using the .ap extention calls an FDP component.
解决方案
1
Below is a sample FDP.xnf file which can also be used in place of an FDP.edn file. Save the text between the dotted lines as a text file named FDP.xnf --------------------------------------------------- LCANET, 6 PROG, handXNF, 5.2.0, "created Fri Apr 23, 1999" PART, 3000 SYM, inv1, INV, SCHNM=INV, LIBVER=2.0.0 PIN, I, I, D PIN, O, O, inflop END SYM, flipflop, DFF, SCHNM=FDCE, LIBVER=2.0.0 PIN, C, I, C PIN, CE, I, vcc PIN, CLR, I, PRE PIN, D, I, flop_D PIN, Q, O, flop_Q END SYM, inv2, INV, SCHNM=INV, LIBVER=2.0.0 PIN, I, I, flop_Q PIN, O, O, Q END PWR, 1, vcc EOF ---------------------------------------------------
2
The workaround to this problem is to use the .ap extention to preset the initial state and then create an FDP.edn file. An FDP.edn file can be created with Foundation schematic capture by selecting the FDP component and generating a netlist from it. The FDP.edn file must be located where the design.edn file is located.