Omron CJ2 - 02-2010 User Manual page 125

DELIVER COMMAND: CMND(490), TRANSMIT: TXD(236), RECEIVE: RXD(235), and PROTO-
COL MACRO: PMCR(260), EXPLICIT MESSAGE SEND: EXPLT(270), EXPLICIT GET
ATTRIBUTE: EGATR(271), EXPLICIT SET ATTRIBUTE: ESATR(272), EXPLICIT WORD READ:
ECHRD(273), EXPLICIT WORD WRITE: ECHWR(274), TRANSMIT VIA SERIAL COMMUNICA-
TIONS UNIT: TXDU(256), and RECEIVE VIA SERIAL COMMUNICATIONS UNIT: RXDU(255).
• The following instructions cannot be used in interrupt tasks when high-speed interrupts are
enabled in the PLC Setup of a CJ2H CPU Unit. An error will occur if any of them are executed.
SELECT EM BANK (EMBC(281)), NETWORK SEND (SEND(090)), NETWORK RECEIVE
(RECV(098)), DELIVER COMMAND (CMND(490)), PROTOCOL MACRO (PMCR(260)), TRANS-
MIT VIA SERIAL COMMUNICATIONS UNIT (TXDU(256)), RECEIVE VIA SERIAL COMMUNICA-
TIONS UNIT (RXDU(255)), EXPLICIT MESSAGE SEND (EXPLT(720)), EXPLICIT GET
ATTRIBUTE (EGATR(721)), EXPLICIT SET ATTRIBUTE (ESATR(722)), EXPLICIT WORD READ
(ECHRD(723), and EXPLICIT WORD WRITE (ECHWR(724))
An instruction processing error will also occur for table data processing instructions, character
string processing instructions, or data shift instructions if background processing is specified in
the PLC Setup.
Additional Information
Relationship of Tasks to Timer Operation
Timer instructions operate as follows:
• Timer Numbers 0 to 2047
Timer present values will continue to be updated even if the task containing the timer is
changed to STANDBY status or is returned to READY status. If the task containing an active
TIM instruction goes to STANDBY status and the present value is 0 when the task returns to
READY status, the Completion Flag will turn ON as soon as the TIM instruction is executed.
(Completion Flags for timers are updated only when the instruction is executed.) The present
value will continue to be updated.
• Timer Numbers 2048 to 4095
The present values of timers that have been started in a task will not be updated while the task
is in STANDBY status. There is a setting in the PLC properties, however, that can be used to
enable the same operation for timers 2048 to 4095 as for timers 0 to 2047.
Relationship of Tasks to Condition Flags
All Condition Flags will be cleared before execution of each task. Therefore Condition Flag status
at the end of task 1 cannot be read in task 2. CCS(282) and CCL(283) can be used to read Con-
dition Flag status from another part of the program, e.g., from another task.
Precautions on Interrupt Tasks
Interrupt Task Priority
Execution of another interrupt task will be stopped to allow the power OFF interrupt task to execute.
The CPU Unit will be reset, but the stopped interrupt task will not be executed after the execution of
the power OFF interrupt task.
The priority for other interrupt tasks is described in the following sections.
Multiple Interrupts Occurring Simultaneously
Interrupt tasks other than power OFF interrupt tasks will be executed in the following order of priority
whenever multiple interrupts occur simultaneously.
I/O interrupt tasks > External interrupt tasks > Scheduled interrupt tasks
Each of the various types of interrupt task will be executed in order starting from the lowest number
if more than one occurs.
CJ2 CPU Unit Software User's Manual
5 Understanding Programming
5
5-35