Wavetronix Click 500 (programmable controller) (CLK-500) - Developer Guide - Manual (Page 79)

78 CHAPTER 8 • SERIAL MESSAGE SUPPORT
Message creation and transmission is handled by the developer through system function
calls. The Click 500 supports targeted protocol reception using a message watch list. The
developer populates this list with the message types to listen for, along with appropriate
callback functions and checksum handlers. Upon receiving a message, the Click 500 has a
receive message processor that makes sure the message (see Figure 8.1):
˽ Was received from the assigned virtual port.
˽ Matches all literal bytes throughout the message.
˽ Has data in the specified variable fields.
˽ Verifies that message integrity with a checksum.
If a message from the watch list is detected and validated then the following will occur:
1 Any data in the variable fields will be extracted and placed in variable memory associ-
ated with the name tag.
2 The assigned callback function will be immediately executed during interrupt time.
Virtual Port Receive
Data Streams
Receive Message Processor
V1 V2 V3 V4
 Match assigned port
 Match literal bytes
 Match variable fields
 Verify checksum
Protocol A Message 2
Protocol A Message 3
. . .
Protocol A Message 1
Protocol Z Message 2
Protocol Z Message 3
Protocol Z Message 1
Message Watch List
1. Extract data from variable fields
2. Execute assigned callback function
Figure 8.1 – Receive Message Processor Diagram
Note
Since callback functions are executed during interrupt time, consider limiting the
amount of code in the callback function. For example, you may be able to pass any
received variable data to an idle loop processing routine via a global structure.