Background Information; Buffering - Husky MP2500 Manual

This chapter is mainly concerned with setting up and using these MP2500
facilities. For more details of standard IBM PC communications, refer to any
standard MS-DOS user's or programmer's guide.
The MP2500 is provided with a built-in file transfer utility called HCOM.COM
and an XMODEM file loader called XL.COM. For details, see Chapter 14.
Alternatively, in many cases you will be able to use a third party
communications package, providing it will operate on IBM PC-compatible
hardware. In this case, MP2500 communications will be completely ignored;
the package will use the serial ports as it would on an IBM PC.

13.3 Background information

You do not need a detailed understanding of data communications to use
the powerful facilities. You simply need to know how to:
•
Connect to the remote system.
•
Set up the MP2500 communications to suit the remote system.
•
Use the communications facilities provided.
The following sections assume that you are using the MP2500 serial
communications port.

13.3.1 Buffering

Port 1 is interfaced via a 16450 UART, without any on-chip buffering.
MP2500 communications provides data buffering via invisible 'buffers' that
effectively disconnect the application program from the outside world. The
communications package is driven by interrupts, for maximum efficiency.
This ensures a smooth flow of data and correct handling of communications
even when the MP2500 is busy doing something quite different!
Because the communication package is interrupt driven, the execution of
user programs is generally not affected by communications. However, the
user program may slow down if the serial line is busy. The buffers are
available whenever the machine is powered up, even if the application
program is not requesting communication. Incoming messages will be
received and held in the buffer, while any outgoing data remaining will
Chapter 13: Introduction to Communications 121