Management of Exchanges and Reports with Explicit Objects

At a Glance

When data is exchanged between the PLC memory and the module, the module may require several task cycles to acknowledge this information.

All IODDTs use two words to manage exchanges:

EXCH_STS (%MWr.m.c.0) : exchange in progress.
EXCH_RPT (%MWr.m.c.1) : report.

NOTE:

Depending on the localization of the module, the management of the explicit exchanges (%MW0.0.MOD.0.0 for example) will not be detected by the application:

for in-rack modules, explicit exchanges are done immediately on the local PLC Bus and are finished before the end of the execution task, so the READ_STS, for example, is always finished when the %MW0.0.mod.0.0 bit is checked by the application.
for remote bus (Fipio for example), explicit exchanges are not synchronous with the execution task, so the detection is possible by the application.

Illustration

The illustration below shows the different significant bits for managing exchanges:

Description of Significant Bits

Each bit of the words EXCH_STS (%MWr.m.c.0) and EXCH_RPT (%MWr.m.c.1) is associated with a parameter type:

Rank 0 bits are associated with the status parameters:
- The STS_IN_PROGR bit (%MWr.m.c.0.0) indicates whether a read request for the status words is in progress.
- The STS_ERR bit (%MWr.m.c.1.0) specifies whether a read request for the status words is accepted by the module channel.
Rank 1 bits are associated with the command parameters:
- The CMD_IN_PROGR bit (%MWr.m.c.0.1) indicates whether command parameters are being sent to the module channel.
- The CMD_ERR bit (%MWr.m.c.1.1) indicates whether or not the command parameters are accepted by the module channel.

NOTE: r corresponds to the number of the rack and m to the position of the module in the rack, while c corresponds to the channel number in the module.

NOTE: Exchange and report words also exist at module level EXCH_STS (%MWr.m.MOD.0) and EXCH_RPT (%MWr.m.MOD.1) as per T_GEN_MOD type IODDTs.

Explicit Exchange Execution Flags: EXCH_STS

The table below shows the EXCH_STS word (%MWr.m.c.0) explicit exchange control bits:

Standard symbol	Type	Access	Meaning	Address
STS_IN_PROGR	BOOL	R	Reading of channel status words in progress	%MWr.m.c.0.0
CMD_IN_PROGR	BOOL	R	Command parameters exchange in progress	%MWr.m.c.0.1
ADJ_IN_PROGR	BOOL	R	Adjust parameters exchange in progress	%MWr.m.c.0.2
RECONF_IN_PROGR	BOOL	R	Reconfiguration of the module in progress	%MWr.m.c.0.15

NOTE: If the module is not present or is disconnected, exchanges using explicit objects (READ_STS, for example) are not sent to the processor (STS_IN_PROG (%MWr.m.c.0.0) = 0), but the words are refreshed.

Explicit Exchange Report: EXCH_RPT

The table below shows the EXCH_RPT (%MWr.m.c.1) word report bits:

Standard symbol	Type	Access	Meaning	Address
STS_ERR	BOOL	R	Detected error reading channel status words (1 = Detected failure)	%MWr.m.c.1.0
CMD_ERR	BOOL	R	Detected error during a command parameter exchange (1 = Detected failure)	%MWr.m.c.1.1
ADJ_ERR	BOOL	R	Interruptions while exchanging adjustment parameters (1 = Detected failure)	%MWr.m.c.1.2
RECONF_ERR	BOOL	R	Interruptions during reconfiguration of the channel (1 = Detected failure)	%MWr.m.c.1.15