st
J a
RESB 0x1000
a J st
END 0
When this program is assembled the J 1003 doesn't fit into 11 bits, and so Sic.asm is forced to pick another addressing mode other than PC-rel.
When simple mode also fails (0x1003) doesn't fit into 12 bits, it picks sic mode.
00000 3C1003 st J a
00003 00....00 RESB 4096
01003 3F0000 a J st
01006 END 0
which Sic.sim incorrectly disassembles to:

When this program is assembled the J 1003 doesn't fit into 11 bits, and so Sic.asm is forced to pick another addressing mode other than PC-rel.
When simple mode also fails (0x1003) doesn't fit into 12 bits, it picks sic mode.
which Sic.sim incorrectly disassembles to: