Posted on December 31, 2016 at 11:38Look guys I know modbus RTU can be implemented on anything really, but I am talking specifically about the hardware modbus support that the newer STM32 bit chips provide.
Here is the description from RM0091:
26.5.8 Modbus communication
The USART offers basic support for the implementation of Modbus/RTU and Modbus/ASCII
protocols. Modbus/RTU is a half duplex, block transfer protocol. The control part of the
protocol (address recognition, block integrity control and command interpretation) must be
implemented in software.
The USART offers basic support for the end of the block detection, without software
overhead or other resources.
Modbus/RTU
In this mode, the end of one block is recognized by a “silence� (idle line) for more than 2
character times. This function is implemented through the programmable timeout function.
The timeout function and interrupt must be activated, through the RTOEN bit in the
USARTx_CR2 register and the RTOIE in the USARTx_CR1 register. The value
corresponding to a timeout of 2 character times (for example 22 x bit duration) must be programmed in the RTO register. when the receive line is idle for this duration, after the last
stop bit is received, an interrupt is generated, informing the software that the current block
reception is completed.
Modbus/ASCII
In this mode, the end of a block is recognized by a specific (CR/LF) character sequence.
The USART manages this mechanism using the character match function.
By programming the LF ASCII code in the ADD[7:0] field and by activating the character
match interrupt (CMIE=1), the software is informed when a LF has been received and can
check the CR/LF in the DMA buffer.
Thus I wanted to know either there is any list of devices that consist of this functionality.
