User`s guide

Aironet Wireless Communications, Inc. 8-1 Confidential and Proprietary
8
CHAPTER 8 A
PLAP Serial Client Software Interface
This chapter details the Peripheral Link Access Protocol (PLAP) software interface to the PC4500/4800
when using serial mode.
Introduction
PLAP is a half-duplex formalized handshaking method of transferring data. The PC4500/4800 processor
connects like a peripheral device to a host PC’s asynchronous serial port. The serial connection must
operate at a single standard baud rate in the range of 7200bit/s to 115.2kbit/s. The interface is designed
to be symmetrical, that is, it will look the same from either end of the connection. Thus, the
PC4500/4800 and the driver on a host PC will use the same frame formats to communicate with each
other.
Serial port settings: 8 bits, No-parity, 2-stop bits
Supported rates: 7.2, 9.6, 14.4, 19.2, 28.8, 38.4, 57.6, 76.8, 115.2 kbit/s
Note: The PC4800 is limited to 2 Mb/s or less as a radio supported rate in serial mode.
Media Access Control
Communication between PLAP layers on a PC4500/4800 and the host PC takes on the form of data and
control frames transmitted over a peripheral line. Media access is simply "transmit if ready and only if
media is not busy." "Busy" is defined as the BUSY_IN line of the serial interface being active (host PC
perspective). There is no immediate confirmation of frame delivery. Once the closing byte of the frame
has been sent, transmission is assumed successful. The nature of a cabled serial interface is such that it