Echelon I/O Model Reference for Smart Transceivers and Neu Instrukcja Użytkownika Pobierz pdf (Strona 111)

I/O Model Reference 101

If you do not specify the #pragma specify_io_clock compiler directive, the

compiler uses a default I/O clock rate of 10 MHz.

Syntax

IO_8 sci [baud (

const-expr

)] [twostopbits] [parity (

parity-expr

)]

io-object-name

;

baud (

const-expr

)

Optionally specifies the serial bit rate through use of the enumeration values

found in the <io_types.h> include file. These enumeration values are:

• SCI_300

• SCI_600

• SCI_1200

• SCI_2400

• SCI_4800

• SCI_9600

• SCI_19200

• SCI_38400

• SCI_57600

• SCI_115200

The enumeration values select serial bit rates of 300, 600, 1200, 2400, 4800,

9600, 19200, 38400, 57600, and 115200, respectively. This clause is optional

in the declaration, but, if omitted, the io_set_baud( ) function must be used.

These bit rates are accurate for devices running at input or system clock

rates that are a multiple of 2.5 MHz. Devices using the 6.5536 MHz clock

rate can be inaccurate (off by more than 3%) at baud rates of 38400 and

higher because the bit rate divisor has been optimized for input clocks that

are a multiple of 2.5 MHz.

twostopbits

Set this option to use two stop bits. By default, there is one stop bit.

You cannot use two stop bits if you also specify even or odd parity. That is, to

use two stop bits, you must specify __parity(none).

This keyword is not supported for Series 5000 devices.

__parity (

parity-expr

)

Specifies optional parity for the serial communications. A parity bit ensures

that the number of “1” bits between the start and stop bits is always even or

odd. Using parity allows you to perform error checking of the

communications channel.

The

parity-expr

can be one of the following values: none, odd, or even.

__parity(none) is the default.

The use of parity is supported only for Series 5000 devices.

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