NEC V850E/CA1 ATOMIC, Preliminary User'S Manual

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Chapter 13 FCAN Interface Function
Preliminary User’s Manual U14913EE1V0UM00
Figure 13-50: Event Processing by ELISA
The flowchart in Figure 13-50 shows the event processing. Some implementations of ELISA limit the
maximum number of commands, which can be executed within one event processing.
Similar to a microcomputer's program counter, ELISA has a temporary command pointer (M_EVTm3).
The temporary command pointer stores the number of the command under execution. Contrary to a
program counter, which holds an absolute address, the command number is an offset relative to the
first command of the command list. The absolute number of the first command is defined by M_EVTm0.
Under normal termination of a command list M_EVTm3 is cleared. In case of a command execution
error, M_EVTm3 contains the number of the command that led to the erroneous execution.
At the beginning of processing a command list ELISA adds the value of M_EVTm3 to the value of
M_EVTm0. That technique allows the user to design a convenient error recovery procedure.
For example: In an application where the full execution of a command list is required to assure data
consistency, a command list once terminated can be continued at exactly the same command, where
the error occurred. Details are described in the following example for event processing of ELISA.
Start Event
Processing
Load and execute
command
END bit set?
- Allow other
modules to access
CAN Memory
CNT = CNT+1
CNT > MAX?
no
no
Execution
Error?
no
End Event
Processing
Start Error
Processing
yes
yes
yes
Message
Event?
CNT = 0
Cnt = Temporary
event pointer
yes
no