Multiplex serial data communications with a single UART for a postage meter mailing machine system

摘要

A postage meter mailing machine includes a multiplex serial data communication system for providing communication between the postage meter mailing machine and a plurality of internal and external devices. Each device can generate and receive serial messages at a respective device communication port. The mailing machine includes a controller, a UART controller module responsive to control signals from the controller, a message buffer in bus communication with the UART controller and a communication multiplexer. The communication multiplexer provides single channel communication with the UART controller module and selectively with one of a number of external communication ports. The communication multiplexer is responsive to control signals from the controller for establishing a communication path between the UART controller module and the selected one of communication ports over the single channel communication and sequentially alternating the communication path between each of the communication ports. Each communication port of the communication multiplexer is directed to a respective one of the device communication ports. The UART controller module can determine whether a serial message data is presented at a respective one of the communication ports and maintaining communication between that communication port and the single channel communication. Messages are directed to and from a buffer until the messaging is completed in the message buffer. When the messaging is complete, the communication multiplexer resumes its cycling between the various communication ports.