AR# 2884: ** OBSOLETE ** M1.3: Map removes IBUF along with unused OBUFT in a bidirectional I/O
AR# 2884
** OBSOLETE ** M1.3: Map removes IBUF along with unused OBUFT in a bidirectional I/O
Description
Keywords: remove, bidirectional, unused
Urgency: standard
General description: Map removes an IBUF along with the unused OBUFT in a bidirectional I/O pin.
解决方案
1
This problem was observed when the OBUFT was embedded under an user-generated XNF output macro in which the pin corresponding to the output of the OBUFT had been assigned a direction of "O" when it was instantiated in the design. NGDBUILD is unable to determine that the underlying output pin is bidirectional, and ends up trimming the IBUF along with the unused OBUFT.
Example. Given the following output macro instantiation with the pin direction of the "O" pin specified as "O" (PIN, O, O, PAD_A):
SYM, Output_A, OBUFTPUF, LIBVER=2.0.0 PIN, O, O, PAD_A PIN, I, I, GND PIN, T, I, VCC END
Change the "O" to a "B" to give:
PIN, O, B, PAD_A
Modified instantiation:
SYM, Output_A, OBUFTPUF, LIBVER=2.0.0 PIN, O, B, PAD_A PIN, I, I, GND PIN, T, I, VCC END
This problem will be fixed in the M1.4 release through a modification of the XNF2NGD program. However, it cannot be fixed in the M1.3 release, and customers must use this workaround.