DESCRIPTION
The ST78C34 is a monolithic Bidirectional Parallel port designed to operate as a general purpose I/O port. It contains all the necessary input/output signals to be configured as a CENTRONICS printer port.
The ST78C34 is a general purpose input/output controller with 83 byte internal FIFO. FIFO operation can be enabled or disabled. For CENTRONICS printer operation, all registers are mapped to IBM printer port registers.
The ST78C34 is designed to operate as normal printer interface without any additional settings. Contents of the FIFO will be cleared after reset or setting the INIT pin to a low state. The auto FIFO operation starts after the first -ACK is received from the printer. Contents of the FIFO transfer to the printer at the printer loading speed.

FEATURES
 • 83 bytes of printer output FIFO
 • Bi-directional software parallel port
 • Bi-directional I/O ports
 • Register compatible to IBM XT, AT, compatible 386, 486
 • Selectable interrupt polarity
 • Selectable FIFO interrupts