The ACL-7122 is a 144-CH high-density parallel digital I/O board for ISA bus. This board provides 6 sets of 24-CH I/O interface. Every 24-CH interface emulates mode 0 of the industry standard 8255 Programmable Peripheral Interface (PPI) chips, each offers three 8-bit ports: PA, PB, and PC. PC is subdivided into 2 nibble-wide (4-bit) ports. Each PPI channel has an individual connector with OPTO-22 pin assignment.