Application Note

Application Note
[Document ID]
AS505xA
Error Monitoring
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
Content Guide
1
General Description ............................................................................................................. 2
2
Detection .............................................................................................................................. 3
3
Analysis ................................................................................................................................ 5
3.1
Error flags ............................................................................................................................. 5
3.1.1
Alarm bits ............................................................................................................................. 5
3.1.2
Communication error flag ..................................................................................................... 6
3.2
Error Status Register............................................................................................................ 7
3.2.1
Description of the error flags ................................................................................................ 7
4
Troubleshooting ................................................................................................................... 9
4.1
Error Avoidance ................................................................................................................... 9
4.2
Clear Error Flag .................................................................................................................. 10
5
Contact Information ............................................................................................................ 11
6
Copyrights & Disclaimer ..................................................................................................... 12
Revision History
Revision
Date
Owner
Description
1.0
26.11.2012
ekno
Initial Version
1.1
24.01.2013
ekno
added more information of WOW and MODE
1.2
05.03.2013
ekno
Correction of WOW description
1.3
21.11.2013
mzie
Apply corporate template, correction of Error
Status Register, general overhaul
1.4
21.10.2014
mzie
Update to new corporate template, adaption to
datasheet
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
1
General Description
The AS5050A and AS5055A offer error monitoring qualities. When an error occurs (e.g.: wrong
clock cycle) the IC detects the failure and gives back an error flag on the SPI interface.
This Application note describes the error flag and how to read out the ICs error status. Furthermore
the different meanings of error flags which can occur are described and also how to avoid errors in
future.
The aim of this application Note is to increase quality of a system during evaluation phase.
2
Detection
Transmission1
Transmission2
SS
SCK
MOSI
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
x x x x x x x x
x x x x x x x x
MISO
x x x x x x x x
x x x x x x x x
0 0 0 0 1 1 0 0
1 1 1 1 0 0 0 0
Figure 1: Normal transmission
In the first transmission an ANGULAR DATA command package is sent (MOSI). The IC answers at
transmission 2 with an ANGULAR DATA read package (MISO).
The content from a normal ANGULAR DATA command package on MOSI signal is shown in Table
1: ANGULAR DATA command package.
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
Bit
15
14
Description
R/W
Content
1
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address <14:1>
1
1
1
1
1
1
1
1
PAR
1
1
1
1
1
1
Bit
Name
Description
15
R/W
0=Write, 1=Read
14:1
Address
14 bit address to read or write
0
PAR
Parity bit (even) calculated on the upper 15 bits
1
Table 1: ANGULAR DATA command package
The content of normal ANGULAR DATA read package on MISO signal is shown in
Table 2: ANGULAR DATA read package. In this case no error occurred.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
Description
Alarm Lo
Alarm Hi
Content
0
0
Bit
Name
Description
15
Alarm Lo
Alarm flag, which indicates a too low magnetic field (details see chapter
“Analysis”)
14
Alarm Hi
Alarm flag, which indicates a too high magnetic field (details see chapter
“Analysis”)
13:2
Angle
Value
Angular value in binary code
1
EF
Error flag, which indicates that an error occurred (details see chapter
“Analysis”)
0
PAR
Parity bit (even = ‘0’ and odd = ‘1’)
Angle Value <13:2>
X
X
X
X
X
X
X
X
X
X
X
X
1
0
EF
PAR
0
X
Table 2: ANGULAR DATA read package
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
3
Analysis
3.1
Error flags
3.1.1 Alarm bits
In case one of the Alarm bits is high, a system error occurred. Both alarm bits set to high indicate a
major system error.
SS
SCK
MOSI
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
MISO
1
1
0
0
1
1
0
0
1
1
1
1
0
0
0
0
Figure 2: both Alarm bits = high
Alarm
Hi
Alarm
Lo
Description
AGC value
0
0
AGC level is higher than the minimum value and lower than the
maximum value.
>0 and <63
0
1
AGC level is equal or even higher than the maximum level.
Magnetic field too weak.
>63
1
0
AGC level is equal or even lower than the minimum level.
Magnetic field too strong.
<0
1
1
Indicates of a major system error has occurred or if the WOW
flag is active. (Error flags can be read out with the error status
register)
Table 3: Alarm bits
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
3.1.2 Communication error flag
The Communication Error Flag (EF) occurs when the SPI communication is incorrect.
The error flag remains until the microcontroller sends a CLEAR ERROR FLAG command.
SS
SCK
MOSI
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
MISO
0
0
0
0
1
1
0
0
1
1
1
1
0
0
1
1
Figure 3: EF = high
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
3.2
Error Status Register
For all detailed information about the error flags and system monitoring read out the error status
register (0x335A). Table 4: Error Status Register (0x335A) shows the Error Status Register.
Bit
Description
Type
13
Reserved
12
FIELD_ALARM_LO
11
FIELD_ALARM_HI
Error Status DSP
10
RANGE
9
CORDICOV
8
ADCOV
7
Reserved
6
Reserved
Error Status System
5
Reserved
4
WOW
3
Reserved
2
ADDMON
Error Status SPI
1
CLKMON
0
PARITY
Table 4: Error Status Register (0x335A)
3.2.1 Description of the error flags
FIELD_ALARM_LO:
AGC level is equal or even higher than the maximum level. Magnetic field is too weak.
FIELD_ALARM_HI:
AGC level is equal or even lower than the minimum level. Magnetic field is too strong.
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[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
RANGE:
The Hall element is driven by a current source. In case of higher temperature, the voltage drop over
the source decreases. The hall element does not fail, but the accuracy is getting worse. To ensure
high system integrity the voltage drop over the current source is monitored.
CORDICOV:
The CORDIC calculates the angle. The error occurs when the input signals of CORDIC are too
large. The internal algorithm fails.
ADCOV:
In case of magnet displacement the IC is not able to capture the whole information of the magnetic
field. Some information gets cut off, because the values are too high.
WOW:
This is a handshake mechanism to check system integrity. By sending a READ ANGLE command
the internal flag (WOW) is set to high. At the end of measurement the WOW is set to low again. In
failure case (internal dead lock situation) the WOW flag remains high.
ADDMON:
In case the microcontroller sends a wrong/not existing address, the sensor reacts with setting this
flag to high.
CLKMON:
The IC is counting the clock cycles. In case the microcontroller sends too much or less clock
samples than standard, the sensor reacts with setting this flag to high.
PARITY:
In case the transmitted parity bit does not match to internally calculated parity bit, the sensor reacts
with setting this flag to high.
Note:
While the IC is busy, the WOW flag is set to high. Therefore the alarm bits are also 1! This indicates
that the IC is still busy. After the IC was busy, the Alarm bits will automatically set to 0. No “Clear
Error Flag” Command is needed.
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
4
Troubleshooting
4.1
Error Avoidance
FIELD_ALARM_LO:
This means that magnetic field is too weak. Decreasing the air gap or choosing a magnet with
higher magnetic field strength can solve this problem.
FIELD_ALARM_HI:
This means that magnetic field is too high. Increasing the air gap or choosing a magnet with lower
magnetic field strength can solve this problem.
RANGE:
The main reason of this error is higher temperature. Decreasing the temperature can be a solution,
but often not possible. Therefore another solution is increasing the magnetic field. This will lower the
voltage drop over the current source of the hall element.
CORDICOV:
This error has several reasons: disturbing external field; magnetic field is too high or large
displacement. When there is an external field disturbing the IC, it can help to start the measurement
again. Otherwise the external field must be eliminated.
A high magnetic field can occur with a “powerful” magnet or less air gap. In both cases the IC sees
a high magnetic field. By changing the air gap or choosing a magnet with another magnetization the
error can be avoided.
Large displacement has nearly the same effect like a high intensive magnetic field. Centering the
magnet and the IC in the rotation axis can also avoid this error.
ADCOV:
This error flag means that there is a displacement between IC and magnet. The best performance
of IC is reached with a centered magnet.
WOW:
When the WOW stays high after 500µs the system integrity is not more given. (Internal dead lock
situation).
ams Application Note, Confidential
[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
4.2
Clear Error Flag
If the Communication Error Flag (EF) is set to high because of a communication problem, the flag
remains set until it will be cleared by a CLEAR ERROR FLAG command. (0x3380)
Bit
15
Description
R/W
Content
1
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Address <14:1>
1
1
0
0
1
1
1
0
PAR
0
0
0
0
0
0
Table 5: CLEAR ERROR FLAG command (0x3380)
SS
SCK
MOSI
1
1
1
0
0
1
1
1
0
0
0
0
0
0
0
0
MISO
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Figure 4: CLEAR ERROR FLAG command (0x3380)
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[v1-4] 2014-Oct-21
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AS505xA – Error Monitoring
5
Contact Information
Buy our products or get free samples online at:
www.ams.com/ICdirect
Technical Support is available at:
www.ams.com/Technical-Support
Provide feedback about this document at:
www.ams.com/Document-Feedback
For further information and requests, e-mail us at:
[email protected]
For sales offices, distributors and representatives, please visit:
www.ams.com/contact
Headquarters
ams AG
Tobelbaderstrasse 30
8141 Unterpremstaetten
Austria, Europe
Tel: +43 (0) 3136 500 0
Website: www.ams.com
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[v1-4] 2014-Oct-21
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6
Copyrights & Disclaimer
Copyright ams AG, Tobelbader Strasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks
Registered. All rights reserved. The material herein may not be reproduced, adapted, merged,
translated, stored, or used without the prior written consent of the copyright owner.
Information in this document is believed to be accurate and reliable. However, ams AG does not
give any representations or warranties, expressed or implied, as to the accuracy or completeness of
such information and shall have no liability for the consequences of use of such information.
Applications that are described herein are for illustrative purposes only. ams AG makes no
representation or warranty that such applications will be appropriate for the specified use without
further testing or modification. ams AG takes no responsibility for the design, operation and testing
of the applications and end-products as well as assistance with the applications or end-product
designs when using ams AG products. ams AG is not liable for the suitability and fit of ams AG
products in applications and end-products planned.
ams AG shall not be liable to recipient or any third party for any damages, including but not limited
to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect,
special, incidental or consequential damages, of any kind, in connection with or arising out of the
furnishing, performance or use of the technical data or applications described herein. No obligation
or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or
other services.
ams AG reserves the right to change information in this document at any time and without notice.
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