The PCI-1737U/PCI-1739U is a 24/48-bit DI/O card with PCI bus. It provides you with 24/48 bits of parallel digital input/output. It emulates mode 0 of the 8255 PPI chip, but the buffered circuits offer a higher driving capability than the 8255. The I/O bits are divided into three 8-bit I/O ports: A0, B0, and C0.( Six for PCI-1739U, A0, A1, B0, B1, C0, C1) You can configure each port as either input or output via software.