Int 7A Fn FDCB  - IBM Personal Communications/3270 - Installation Check    [I]

   AX = FDCBh

Return: DX:AX -> PCS/3270 signature block if loaded (see below)

Format of signature block:
Offset Size    Description
 04h   WORD    PCS/3270 signature (5741h)
 06h   WORD    version (0501h = PCS/3270 v1.0)