Oki JOB60851 User Manual

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Oki JOB60851 User Manual Manual pdf 61 page image

Chapter 4 Software Developmentpage 4-264-5. Standard I/O over Serial LinkSection 2-.3 "Running User Programs" downloaded and executed a simple "Hello world!" programthat displays its message on the personal computer screen.C compilers for personal computers assign a keyboard to the standard input and a monitor to thestandard output. The JOB60851 board has neither, but the programmer can provide substitutes asdescribed in this section.4-5-1. JOB60851 Board Standard I/OThe sample file stdrw573.c maps the JOB60851 board's standard input and output to a serial linkjoining a terminal emulator running on the host personal computer to an MSM66Q573 serial port onthe JOB60851 board.Standard input: Data from terminal emulator to MSM66Q573 RX pinStandard output: Data to terminal emulator from MSM66Q573 TX pinThe functions required to create these mappings are read() and write(). Because of their tight linkswith hardware, these are known as low-level functions (as opposed to high-level functions withoutsuch dependencies).Figure 4.5.1 summarizes the data flows for the resulting I/O.C language I/O functionsLow-level standard I/O libraryfunctions read() and write()MSM66Q573 serial portTerminal emulator running onpersonal computergetchar(), putchar(), and similar standardlibrary functions (high-level standard I/Olibrary functions)High-level output functions write their datawith write(). High-level input functions readtheir data with read().TX data from write().RX data to read().(Only SIO0 used)Data received: from MSM66Q573 TX pinData transmitted: to MSM66Q573 RX pinFigure 4.5.1. JOB60851 Board Standard I/OTable 4.5.1 shows the dependencies on these two low-level functions by the higher-level I/Ofunctions included in the standard libraries for the JOB60851 board C compiler (cc665s). Because ofthese dependencies, be sure to include the corresponding source code file (stdrw573.c) on thecompiler command line.