Programmable printer

A programmable printer is provided which is capable of printing alphanumeric internally pre-stored data or data information and alphanumeric externally supplied data or data information either separately or in combination with each other. The alphanumeric printout of the printer may be inverted in a manner to allow its visual reading in what would otherwise be an "upside-down" configuration. The programmable printer incorporates a microprocessor for the proper addressing, interpretation and manipulation of input commands, timing information, paper-sensing information, external data information, and internal stored data information, so as to generate output information that seeks the desired data information, whether external or internal, and that drives a printer logic interface and output status lines and print drive interface so as to print the desired information and to monitor the status of the printer. The printer also includes an alphanumeric print mechanism incorporating twenty-one character columns per line of printout, a timing pulse generating means, a paper sensing means, and a lid detector switch; a printer logic interface that provides electrical isolation between the print mechanism and the microprocessor and provides the actuating power to operate the print mechanism's hammers as well as means for amplifying and shaping the timing pulses and paper sensing pulses from the print mechanism; a command interface that provides electrical isolation between the command information and the microprocessor as well as providing for the proper selection, shaping and timing of the command information; a data interface that provides electrical isolation between the external data information and the microprocessor as well as providing for the proper selection, shaping and timing of external or internal data information; a programmable "read only" memory for the storage of various messages; a set of output status lines for the transmission of information to the outside world and for the indication of various conditions of the printer; and a print drive interface that provides for the electrical isolation, shaping and amplification of the output status lines information and the print drive information.