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SERIAL PORTS SECTION 4

Page 4-2

POWER CONTROL

The RS-232 driver chip U 9 has a shut dow n control to

reduce power (about 10 ma). This line is controlled by

CPU port P4.2. Examples are in RTC-3.C in the RTC

directory.

On power up or reset, the control line automatically goes

high, enabling RS-232. You can save about 10 ma.

current by bringing P4.2 low.

Allow about 1 ms recovery time for U9 before

transmitting characters when P4. 2 is brought back high

(from IDLE mode).

C BUS

The I

C bus uses two wires SDA (available at J3-17) and

SCL (available at J3-15) to transfer information between

devices connected to the bus. Refer to the

8X552OV. PDF data sheet for more programming

information. Detailed information starts on page 3-481.

This bus uses ports P1.6 and P1. 7 which ar e shared with

the LCD display port.

SERIAL PORT PIN OUT

Pin out for J4 is shown below. Unused pins are open.

You can easily make your own cable from 10 pin header

and female DB-9 IDC connectors to a PC. Take a 9

wire ribbon cable and align pin 1 to pin 1 on each

connector and crimp.

J4 pin Name Direction DB-9

from card pin

3 Tx 0 Out 2

4 RTS (Rx 1) In 7 (3)

5 Rx 0 In 3

6 CTS (Tx 1) Out 8 (2)

9 Ground 5

10 +5

Alternate functions and pin out for RTS and CTS are

shown above in parentheses. When used as transmit and

receive, these lines must be broken from the cable and

wired directly to a connector.

The corresponding signal names from the DB-9 are the

opposite of what is coming out of the RPC-220. Thus,

Tx becomes Rx on the PC . CTS becomes RTS on the

PC.

Rx1 and Tx 1 are alternate uses for RTS and CTS lines.

These are the COM1 software serial port lines. The

VTC-29F serial cable connects to the RPC-220 and

breaks out COM0 and COM 1 into two connectors.

APPLICATION PROGRAMS

The following programs are in the SERIAL directory.

File name Description

SOFT .asm Uses software serial port. Baud rates from

300 to 9600. Should not be used with

interrupts.

COM00.C Interrupt driven COM 0 serial routine.

Transmit and receive are buffered.

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 46 47

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Remote-processing RPC-220 Manuale Utente Pagina 22

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