Editing MOS Technology 6522 (section)

==Input/output ports==
The VIA contains 20 I/O lines, which are organised into two 8-bit bidirectional ports (or 16 general-purpose I/O lines) and four control lines (for [[Handshake (computing)|handshaking]] and [[interrupt]] generation). The directions for all 16 general lines (PA0-7, PB0-7) can be programmed independently. The control lines can be programmed to generate an interrupt when activated (all four), latch the corresponding I/O port (CA1 and CB1), automatically generate handshaking signals for devices on the I/O ports, or operate as plain program-controlled outputs (CA2 and CB2).  CB1 and CB2 are also used as the clock input and the data line for the shift register, precluding their use for other functions while the shift register is enabled.