SPI/Microwire-Compatible

UART in QSOP-16

16

______________________________________________________________________________________

MAX3100

3100

IRQ

RX

TX

RX

TX

RXD

TXD

22pF

22pF

330

Ω

IR LED

+5V

1/6 HC00

1/6 HC00

DIRECT

OPTO-COUPLER

DRIVE

OR

IR MODULE

DRIVE

IR

MODULE

8051

MAX3221

100

Ω

0.1

µF

+5V

1.8432MHz

10k

Figure 10. Bidirectional RS-232 IrDA Using an 8051

Interface to PIC Processor

(“Quick Brown Fox” Generator)

Figure 11 illustrates the use of the MAX3100 with the

repeatedly transmits “THE QUICK BROWN FOX JUMPS

OVER THE LAZY DOG” (covering the entire alphabet)

over an RS-232 link with adjustable baud rate, word

length, and delay. Although a software-based UART

could be implemented on the PIC, features like accu-

rate variable baud rates, high baud rates, and simple

protocol selection would be difficult to implement reli-

ably. The 16C54 in the example is the most basic of the

PICs. Thus, it is possible to implement the example on

any member of the PIC family.

The software routine (Figure 12) begins by reading the

DIP switch on port RB. The switch data includes 4 bits

for the baud rate, 1 bit for number of stop bits, 1 bit for

a word length of 7 or 8 bits, and 1 bit for delay between

messages. The PIC reads the switch only at initializa-

tion (reset), and programs the parameters into the

MAX3100. It then begins sending the message repeat-

edly. If the delay bit is set, it inserts a 1sec delay

between transmissions. As in the 8051 example, the

main routine is called UTLK, and can be used in any

PIC-based, port-pin-interfaced application.

PIC is a registered trademark of Microchip Corporation.