Multiprocessor Communications; Programming The Serial Port; Configuring The Serial Port Pins; Programming The Control Register - Intel 8XC196K Series User Manual

8XC196K x , J x , CA USER'S MANUAL
7.3.2.5

Multiprocessor Communications

Modes 2 and 3 are provided for multiprocessor communications. In mode 2, the serial port sets
the RI interrupt pending bit only when the ninth data bit is set. In mode 3, the serial port sets the
RI interrupt pending bit regardless of the value of the ninth bit. The ninth bit is always set in ad-
dress frames and always cleared in data frames.
One way to use these modes for multiprocessor communication is to set the master processor to
mode 3 and the slave processors to mode 2. When the master processor wants to transmit a block
of data to one of several slaves, it sends out an address frame that identifies the target slave. Be-
cause the ninth bit is set, an address frame interrupts all slaves. Each slave examines the address
byte to check whether it is being addressed. The addressed slave switches to mode 3 to receive
the data frames, while the slaves that are not addressed remain in mode 2 and are not interrupted.
7.4

PROGRAMMING THE SERIAL PORT

To use the SIO port, you must configure the port pins to serve as special-function signals and set
up the SIO channel.
7.4.1

Configuring the Serial Port Pins

Before you can use the serial port, you must configure the associated port pins to serve as special-
function signals. Table 7-1 on page 7-2 lists the pins associated with the serial port. Table 7-2 lists
the port configuration registers, and Chapter 6, "I/O Ports," explains how to configure the pins.
7.4.2

Programming the Control Register

The SP_CON register (Figure 7-6) selects the communication mode and enables or disables the
receiver, parity checking, and nine-bit data transmissions. Selecting a new mode resets the serial
I/O port and aborts any transmission or reception in progress on the channel.
7-8