AR# 6057: M1 Map - ERROR:x4kma:7 - The CY4 symbol "$blah" has no signal connected to CIN
M1 Map - ERROR:x4kma:7 - The CY4 symbol "$blah" has no signal connected to CIN
keywords : map, CY4, CIN, x4kma:7
urgency : standard
general description :
Map may produce the following error due to unconnected nets in a design - especially for macros in the library whose CIN block is not connected:
>Removing unused logic... >ERROR:x4kma:7 - The CY4 symbol "$I1/$1I149" (output >signal=$I1/C0) has no signal connected to CIN. This can >only be done with carry-initiating carry modes (those that >are not of the form xxxxx-CI). Please change the carry >mode on this symbol to be a carry-initiating mode, or >connect a CY4 with a carry-initiating mode to the CIN pin >of "CY4 symbol "$I1/$1I149" (output signal=$I1/C0)". >Errors were found in the carry logic. No output files have >been written.
If you don't need the CIN block, it's important that it be tied to a known value such as GND or VCC rather than leaving it floating. In order to also avoid the propagation of optimization during map, the GND or VCC plane should be separated by a register from the CIN input. In other words, drive the CIN input with an FD whose DIN input is tied to VCC or GND, as needed. This will eliminate the error and any undesired optimization.