High-speed reliable parallel data transmission between a computer and a parallel peripheral is provided by a peripheral controller by way of a virtual parallel UART (VPU). The VPU provides a novel parallel interface for higher speed parallel interface operation. The VPU is included in the peripheral controller along with a conventional RS-232 UART. The peripheral-side interface of the peripheral controller provides full bidirectional handshaking with the parallel peripheral. The host-side interface of the peripheral controller provides a legacy serial port compatible interface. Mode information selectively configures operation in either a VPU (parallel) or a UART (serial) mode. Both modes appear identical to software executing on the computer, enabling the use of standard serial I/O drivers without modification, and providing transparent legacy mode compatibility even when the hardware is configured for VPU mode.