90 Appendix WAGO-I/O-SYSTEM 750750-657 IO-Link MasterManualVersion 1.0.2, valid from FW/HW-Version 02/0111.1.2.1.1.3 Control/StateThe communication mechanisms of an "IOL_CALL" runs according to therequest/response operation.The data byte is always "CONTROL" for communication from the control to theI/O module. The CONTROL byte used for this purposes has the followingstructure:Table 51: IOL_CALL, CONTROL data structureBit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 00 CONTROLTable 52: IOL_CALL, CONTROL data structure, descriptionBit field Wert Description0 Cancel /Release IOL_CALL1 IDLE sequence2 Write request3 Read requestCONTROL4…255 ReservedThe data byte is always "STATE" for communication from the I/O module to thecontrol. The STATE byte used for this purposes has the following structure:Table 53: IOL_CALL, Control data structureBit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0IOL_ERROR_PDU0 0 0 0 0 STATETable 54: STATE, DescriptionBit field Value Description0 Data transfer completed1 IDLE sequence2…127 Reserved128 IOL error PDUSTATE128...255 Reserved0 No ErrorIOL_ERROR_PDU 1 ErrorIf the I/O module returns an "IOL_Error_PDU" as the response, extended errorinformation can be taken from the other four bites ("IOL-M_error_code" (2bytes), "IOL-D_error_code" and "IOL-D_(add)_error_code"), see section "ErrorMessages".
