M580 Safety System Bits

System Bits for SAFE Task Execution

The following system bits apply to the M580 safety PAC. For a description of system bits that apply to both the M580 safety PAC and non-safety M580 PACs, refer to the presentation of System Bits in the EcoStruxure™ Control Expert System Bits and Words Reference Manual.

These system bits are related to the execution SAFE task, but are not directly accessible in safety program code. They can be accessed only via the S_SYST_READ_TASK_BIT_MX and S_SYST_RESET_TASK_BIT_MX blocks.

Bit Symbol	Function	Description	Type
%S17 `CARRY`	Rotate shift output	During a rotate shift operation in the SAFE task, this bit takes the state of the outgoing bit.	R/W
%S18 `OVERFLOW`	Overflow or arithmetic error detected	Normally set to 0, this bit is set to 1 in the event of a capacity overflow if there is: A result greater than + 32 767 or less than - 32 768, in single length. A result greater than + 65 535, in unsigned integer. A result greater than + 2 147 483 647 or less than - 2 147 483 648, in double length A result greater than +4 294 967 296, in double length or unsigned integer. Division by 0. The root of a negative number. Forcing to a non-existent step on a drum. Stacking up of an already full register, emptying of an already empty register.	R/W
%S21 `1RSTTASKRUN`	First SAFE task scan in RUN	Tested in the SAFE task, this bit indicates the first cycle of this task. It is set to 1 at the start of the cycle and reset to 0 at the end of the cycle. NOTE: The first cycle of the task status can be read using the `SCOLD` output of the `S_SYST_STAT_MX` system function block. This bit is not effective for M580 Safety Hot Standby systems.	R/W

Bit

Symbol

Function

Description

Initial State

Type

%S17

CARRY

Rotate shift output

During a rotate shift operation in the SAFE task, this bit takes the state of the outgoing bit.

R/W

%S18

OVERFLOW

Overflow or arithmetic error detected

Normally set to 0, this bit is set to 1 in the event of a capacity overflow if there is:

A result greater than + 32 767 or less than - 32 768, in single length.
A result greater than + 65 535, in unsigned integer.
A result greater than + 2 147 483 647 or less than - 2 147 483 648, in double length
A result greater than +4 294 967 296, in double length or unsigned integer.
Division by 0.
The root of a negative number.
Forcing to a non-existent step on a drum.
Stacking up of an already full register, emptying of an already empty register.

R/W

%S21

1RSTTASKRUN

First SAFE task scan in RUN

Tested in the SAFE task, this bit indicates the first cycle of this task. It is set to 1 at the start of the cycle and reset to 0 at the end of the cycle.

NOTE:

The first cycle of the task status can be read using the SCOLD output of the S_SYST_STAT_MX system function block.
This bit is not effective for M580 Safety Hot Standby systems.

R/W

Notes Regarding Non-Safety-Specific System Bits

System Bit	Description	Notes
%S0	cold start	Can be used only in process (non-SAFE) tasks and has no influence on SAFE task.
%S9	outputs set to fallback	Has no influence on Safety output modules.
%S10	Global I/O detected error	Reports some, but not all, of the possible detected errors relating to safety I/O modules.
%S11	watchdog overflow	Takes into account an overrun on SAFE task.
%S16	task I/O detected error	Reports some, but not all, of the possible detected errors relating to safety I/O modules.
%S19	task period overrun	Information for SAFE task overrun is not available.
%S40...47	rack n I/O detected error	Reports some, but not all, of the possible detected errors relating to safety I/O modules.
%S78	STOP on detected error	Applies to both process tasks and the SAFE task. If the bit is set, for example if a %S18 overflow error rises, the SAFE task enters HALT state.
%S94	save adjusted values	Does not apply to SAFE variables. The SAFE initial values are not modifiable by the activation of this bit.
%S117	RIO detected error on Ethernet I/O network	Reports some, but not all, of the possible detected errors relating to safety I/O modules.
%S119	general in rack detected error	Reports some, but not all, of the possible detected errors relating to safety I/O modules.