Mikroelektronika MIKROE-742 데이터 시트

344

- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 6

procedure RS485Slave_Receive(var data_buffer: array[20] of byte);

Nothing.

Receives messages from Master. If Slave address and Message address field
don't match then the message will be discarded. Messages are multi-byte, so
this routine must be called for each byte received. 

Parameters : 

- 

data_buffer

: 6 byte buffer for storing received data, in the following manner: 

- 

data[0..2]

: message content 

- 

data[3]

: number of message bytes received, 1–3 

- 

data[4]

: is set to 255 when message is received 

- 

data[5]

: is set to 255 if error has occurred 

The function automatically adjusts data[4] and data[5] upon every received mes-
sage. These flags need to be cleared by software.

MCU must be initialized as a Slave for RS-485 communication. See
RS485Slave_Init.

var msg : array[20] of byte;
...

RS485Slave_Read(msg);

procedure RS485Slave_Send(var data_buffer: array[20] of byte;
datalen : byte);

Nothing.

Sends message to Master. Message format can be found at the bottom of this page.

Parameters : 

- 

data_buffer

: data to be sent 

- 

datalen

: number of bytes for transmition. Valid values: 0...3. 

MCU must be initialized as a Slave for 

RS-485

communication. See

RS485Slave_Init

. It is the user’s responsibility to ensure (by protocol) that only

one device sends data via 485 bus at a time.

var msg : array[8] of byte;
...
// send 2 bytes of data to the Master

RS485Slave_Send(msg, 2);