Data Transfer - WAGO I/O-SYSTEM 750 Manual

14 • 750-653 (/xxx-xxx) [Serial Interface RS 485]

Data transfer

2.1.1.9 Data transfer
With the control and status byte the controlling of the sending and receive
mode takes place. Requests are indicated by a bit change of state. An assigned
bit indicates execution by adopting the value of the request bit.
Initialization of the module:
• Set IR bit in the control byte
• Initialization of the module
• Transmit/receive functions are blocked
• Output/input buffers are erased
• Serial interface module will load its configuration data
Transmitting data:
• TR=TA: put characters into output bytes
• Amount of characters is specified in OL0 to OL2
• TR is inverted and read out
• Characters are put into output buffer if TR=TA
Receiving data:
• RR≠RA: data in input bytes characters are available
• Amount of characters is specified in IL0 to IL2
• Characters in IL0 to IL2 are read out
• RA is inverted and read out
• All characters are read when RR=RA
The transmitting and receiving of data can be done simultaneously. The
initialization request has priority and will stop transmitting and receiving of
data immediately.
Attention
Resetting the initialization bit can be performed with the following message.
Message: input buffer full (Bit 3)
Input buffer is full. Data which is being currently received is now lost.
WAGO-I/O-SYSTEM 750
I/O Modules