Error on tile port mismatch

[mole99]

Currently, FABulous connects the ports of neighboring tiles based on their order of their occurrence in the .csv file.

For example, consider this N_IO tile:

TILE,N_IO,,,,,
#direction,source_name,X-offset,Y-offset,destination_name,wires,
NORTH,NULL,0,-1,N_GBUF_END,4,# global buffers
SOUTH,S1BEG,0,1,NULL,4,
SOUTH,S2BEG,0,1,NULL,8,
SOUTH,S2BEGb,0,1,NULL,8,
SOUTH,S4BEG,0,4,NULL,4,
SOUTH,SS4BEG,0,4,NULL,4,
NORTH,NULL,0,-1,N1END,4,
NORTH,NULL,0,-1,N2MID,8,
NORTH,NULL,0,-1,N2END,8,
NORTH,NULL,0,-4,N4END,4,
NORTH,NULL,0,-4,NN4END,4,
NORTH,NULL,0,-1,Ci,1,# carry
JUMP,NULL,0,0,GND,1,
JUMP,NULL,0,0,VCC,1,
BEL,../../primitives/IOBUF/rtl/IOBUF.v,A_,,,,
MATRIX,./N_IO_switch_matrix.list,,,,,
EndTILE,,,,,,

This matches the LUT4x8_C tile:

TILE,LUT4x8_C,,,,,#carry out
NORTH,N_GBUF_BEG,0,-1,N_GBUF_END,4,# global buffers
INCLUDE,../common/Base.csv,,,,,
#direction,source_name,X-offset,Y-offset,destination_name,wires,
JUMP,GCLK_BEG,0,0,GCLK_END,1,
JUMP,GSR_BEG,0,0,GSR_END,1,
JUMP,GEN_BEG,0,0,GEN_END,1,
NORTH,CO,0,-1,CI,1,# carry
JUMP,J_SR_BEG,0,0,J_SR_END,1,
JUMP,J_EN_BEG,0,0,J_EN_END,1,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LA_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LB_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LC_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LD_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LE_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LF_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LG_,,,,
BEL,../../primitives/FABULOUS_LC/rtl/FABULOUS_LC.v,LH_,,,,
MATRIX,./LUT4x8_C_switch_matrix.list,,,,,
EndTILE,,,,,,

However, when these two lines are swapped:

INCLUDE,../common/Base.csv,,,,,
NORTH,N_GBUF_BEG,0,-1,N_GBUF_END,4,# global buffers

FABulous will connect the LUT4x8_C's north ports and the N_IO's south ports in a completely wrong order! Don't ask me how I found this out 😅
This should really be matched by name and not by order.

If the ports don't match, FABulous should abort and print an error message.

[KelvinChung2000]

This is likely because we are guessing the connection endpoint, and the guess failed, falling back to order matching.

But this is also a flaw in the tile description. Consider just having the following line:

SOUTH,S2BEG,0,1,NULL,8,

From the tile's perspective, you cannot tell which port it is connected to; it could be any of the wires. The educated guess would be S2END, but this one actually goes to S2MID. So, even name matching does not really work, and to solve this, I think we actually need to update how we describe endpoints.

[KelvinChung2000]

There is a chance it might work if you name them N1BEG_GBUF and N1END_GBUF, since we match that naming convention.

[mole99]

Ah, right! Well, maybe we do need a BEG/END naming convention or something similar that is enforced by FABulous. Or, as you mentioned, a different way of describing endpoints.

[mole99]

There is a chance it might work if you name them N1BEG_GBUF and N1END_GBUF, since we match that naming convention.

Thanks, I'll try that!