Mitsubishi Electric R60AD8-G User Manual page 289

Operation
The following figure shows operation with one time of A/D conversion circuit diagnostics.
SIL2 Process CPU
SIL2 diagnostic FB library
SIL2 safety program FB
SIL2 standard
program FB
No. Description
(1) The SIL2 safety program FB sends a diagnostics start notification to the R60AD8-G.
(2) The R60AD8-G sends a digital value for diagnostics to the SIL2 safety program FB.
(3) The SIL2 standard program FB receives a request from the SIL2 safety program FB, and switches a device that inputs signals to the
R60AD8-G from an input device (such as a sensor) to the R60DA8-G for diagnostics. The switching is performed for each channel used, by
using a relay.
(4) The SIL2 standard program FB receives a request from the SIL2 safety program FB, sets a digital value for diagnostics in the R60DA8-G for
diagnostics, performs digital-analog converting for the digital value, and inputs the value to the R60AD8-G.
(5) The R60AD8-G compares two values: a digital value obtained from A/D conversion on the analog value input from the R60DA8-G for
diagnostics; the digital value for diagnostics. The R60AD8-G verifies whether the error (comparison result) is within the allowable error range
set in "Duplex input error range setting", and sends the verification result to the SIL2 safety program FB.
For channels determined to have an error as a result of verification, an A/D conversion circuit diagnostic error (error code: 1EFH) occurs.
• For verification, the setting value of "Duplex input error range setting" is automatically applied as the
allowable error range. If A/D conversion circuit diagnostic errors occur frequently, adjust the setting of
"Duplex input error range setting".
• When i_bEN (execution command) of the SIL2 safety program FB is turned off, A/D conversion circuit
diagnostics is not executed even when the cycle of A/D conversion circuit diagnostics has elapsed. A/D
conversion circuit diagnostics is executed when i_bEN (execution command) is turned on.
• During A/D conversion circuit diagnostics, the external connection is switched from the sensor to the
R60DA8-G for diagnostics by controlling relay. Digital operation values are not updated and in the safety I/O
HOLD state during A/D conversion circuit diagnostics.
Sensor
Analog input Analog input
CH
R60AD8-G (Sub) R60AD8-G (Sub)
R60AD8-G (Main) R60AD8-G (Main)
Digital Digital
operation value operation value
A/D conversion A/D conversion
circuit diagnostics circuit diagnostics
(1)
(2)
(5)
(4)
(3)
Sensor
Analog output
CH CH
R60DA8-G for R60DA8-G for
diagnostics diagnostics
Digital value
10.8 SIL2 A/D Conversion Function
10
Y
RY40PT5B RY40PT5B
10 FUNCTIONS
287