ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Preliminary
ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Rev. 0.82, Preliminary
This Revision is not valid for earlier revisions than ZMD31050C*.
For parts identification refer ZMD31050 Development Status Report.
Copyright © 2007, ZMD AG, Rev. 0.82, 2007-01-26,
1/46
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Preliminary
Contents
1.
1.1
1.2
1.3
C
ONTROL
L
OGIC
....................................................................................................................... 3
General Description
CMC Description
General Working Modes
3
3
4
2.
2.1
2.2
2.3
2.4
S
IGNAL
C
ONDITIONING
.............................................................................................................. 6
A/D-Conversion
Correction Formula for Measurand (e.g. pressure)
Correction Formula for Temperature
Limiting the Output
6
7
7
8
3.
3.1
3.2
3.3
3.4
O
UTPUTS
................................................................................................................................. 9
General Description
PWM Output
Alarm Tasks
Digital Readout
9
10
12
13
4.
4.1
4.2
4.3
4.4
4.5
S
ERIAL
D
IGITAL
I
NTERFACE
..................................................................................................... 14
General Description
I
2
C Protocol
OWI – OneWire Digital Interface
Synchronous serial peripheral interface (SPI) Introduction
Interface Commands
14
15
18
23
27
5.
5.1
5.2
5.3
5.4
EEPROM &RAM ................................................................................................................... 30
Programming the EEPROM
EEPROM & RAM Contents
EEPROM & RAM Configuration words
EEPROM Signature
30
30
32
38
6.
6.1
6.2
6.3
6.4
T
EMPERATURE
S
ENSOR
A
DAPTION
& CMV M
EASSUREMENT
.................................................... 39
Sensor Bridge in Voltage Mode
Sensor Bridge in Current Mode
TEMP2 Measurements
CMV Measurement
39
42
43
44
7.
7.1
7.2
ADDITIONAL BUILD IN F
EATURES
........................................................................................ 45
Internal Supply Regulator using an external FET
External Clock Input Option
45
45
8.
R
ELATED
D
OCUMENTS
............................................................................................................ 46
Copyright © 2007, ZMD AG, Rev. 0.82, 2007-01-26,
2/46
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Preliminary
1.
1.1
CONTROL LOGIC
General Description
The control logic of the ZMD31050 consists of the Calibration Micro-Controller (CMC) and the modules
control logic of the A/D-Converter, Control logic of the digital Ports, PWM and serial digital Interface.
The configuration of the various modes of the device is done by programming an EEPROM.
The Calibration Micro-Controller controls the measurement cycle and realizes the calculations for
sensor signal conditioning. This eliminates the gain deviation, the offset, the temperature deviation and
the non-linearity of the pre-amplified and A/D-converted sensor signal.
The communication of the ZMD31050 with an external micro-controller especially for calibration
purposes is done via a serial digital interface. Communication protocols according to I
2
C and SPI
standard are supported. Additionally an one wire interface is implemented. These serial interfaces are
used for the calibration of the sensor system consisting of transducer and ZMD31050.
Furthermore the serial interface makes available the read out of the results of sensor signal
conditioning as digital values during the calibration or during the Normal Operation Mode for
processing by an external micro-controller. The internal processing of received interface commands is
done by the CMC. As a consequence the measurement cycle is interrupted if a command is received.
Only the read out of data is controlled by the serial interface itself and does not interrupt the CMC.
The controller of the A/D-conversion is started by the CMC. It generates a clock for the A/D-converter
(switched capacitor technique), the chopper clock for the analog front end and executes a continuous
measurement cycle. The result of the A/D-conversion is a counter value, which is read and processed
after a synchronization signal which is generated after every measurement. The processing of the
conditioning calculation by the CMC works parallel to the A/D-conversion.
The output of the conditioning result can be done via various channels: analog voltage output,
(4 to 20) mA current loop, PWM. Additionally there are two digital output ports with programmable
threshold, hysteresis and delay.
1.2
CMC Description
The
Calibration Micro-Controller
(CMC) is especially adapted to the tasks connecting with the signal
conditioning. The main features are:
•
Processing width 16 Bit
•
•
Programmed via ROM
Constants/coefficients for the conditioning calculation are stored in the EEPROM. After power-on
or after re-initialization from EEPROM by sending a certain command to the serial interface the
EEPROM is mirrored to the RAM.
Continuous parity-check during every read from RAM. If incorrect data is detected, an error mode
is started (error code is written to the serial digital output, the analog out is set to diagnostic
mode).
The conditioning calculation is done with 16 Bit saturation arithmetic, i.e. if an overflow occurs in
any calculation the result is fixed to the maximum of the defined 16Bit range. The sign is
preserved.
•
•
Copyright © 2007, ZMD AG, Rev. 0.82, 2007-01-26,
3/46
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Preliminary
1.3
General Working Modes
Open Mode
Reduced command set
START_CM
START_OM
Command Mode
Full command set
START_NOM
START_NOM
Normal Operation Mode
Reduced command set
Fig. 1
:
1.3.1
Modes of digital serial interface
Normal Operation Mode
The “Normal Operation Mode” (NOM) is the working mode in which the signal condition operation is
done. After power-on the ZMD31050 starts with an initialization routine, which also can be started by
sending a certain command via the serial digital interface at any time. First the EEPROM is mirrored to
the RAM, thereby the EEPROM contents are checked. If an error is detected, the “Command Mode” is
started, the analog output is shifted in the diagnose range and an error code can be read via the digital
interface. Furthermore the configuration of the ZMD31050 is set during initialization. This configuration
evaluates all the configuration data stored in the EEPROM, e.g. measurement cycle, signal output
mode, mode of digital serial interface etc.. After the initialization the continuous measurement cycle,
the conditioning calculation and the output via various channels starts. Provided that the EEPROM is
programmed correct, this mode works without sending any command to the digital serial interface.
1.3.2
Command Mode
The ZMD31050 changes to “Command Mode” (CM) after receiving a correct command via the digital
serial interface. This command generates an interrupt for the CMC, the measurement cycle is stopped
and the called command routine is processed. During processing the serial interface is disabled, no
further commands are recognized. After finishing the routine the CMC waits for further commands. It is
also possible to start the NOM by using the current contents of EEPROM or RAM.
1.3.3
Digital Serial Interface
Regarding the digital serial interface 3 modes are distinguished: the “Open Mode” (OM), the “Normal
Operation Mode” (NOM) and the “Command Mode” (CM). In OM and NOM only a reduced set of
commands is available. For all commands which change the configuration of the ZMD31050 (write to
EEPROM/RAM, start different measurement cycle) the ZMD31050 has to be previously transferred to
CM. This protects the ZMD31050 against unintentional configurations.
After power-on the ZMD31050 starts in Open Mode. Every command sent to the digital serial interface
transfers the ZMD31050 to the Normal Operation Mode except the command START_CM, which starts
the CM. The command START_CM is only processed if it is received as first command after power-on
via digital serial interface. Is the ZMD31050 once changed to NOM, this mode can only be reset by a
new power-on. The ZMD31050 leaves the CM by receiving the commands START_OM or
START_NOM or by reset due to power-on.
Copyright © 2007, ZMD AG, Rev. 0.82, 2007-01-26,
4/46
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
ZMD31050
Advanced Differential Sensor Signal Conditioner
Functional Description
Preliminary
If the ZMD31050 receives a command in NOM, which is not element of the reduced command set, this
command is ignored, no interrupt for the CMC is generated and the measurement cycle is continued. If
the serial interface works in I
2
C mode no acknowledges are generated after the command byte.
1.3.4
Error Codes
The ZMD31050 detects various possible errors. A detected error is signalized by changing in a
diagnostic mode. In this case the analog output is set to High or Low (maximum or minimum possible
output value) and the output registers of the digital serial interface are set to a significant error code
(see Table 1). Note that the error detection functionality has to be partly enabled by configuration
words (Sensor Connection; Common Mode Voltage out of limits).
Detectable
Error
EEPROM
Sign
RAM Parity
Register
Parity
ROM Check
Arithmetic
Check
Watchdog
Configuration
Description
Signature-Check during read out of
EEPROM after Power On or after SIF-
Command COPY_EEP2RAM
Parity-Check at every RAM access
Permanent Parity-Check of Configuration
Registers
Signature-Check of ROM after Power-on
Arithmetic-Check during measurement
cycle
Watchdog-Check of start-routine and
measurement-cycle
Programmed configuration is not allowed
(Conflict regarding A/D-conversion-time
and enabled functionality)
Connection-Check of Sensor Bridge
Check if Bridge Common Mode Voltage
complies the programmed limits
CFGAPP:
SCCD
CGFCYC:
ECMV
CFGAPP:
SCCD
CFGAPP:
SCCD
CFGCYC:
ROMCHE
Enabled by
[Register:Bit]
Sets SIF- Sets Analog Out to <…> for
Out to
Voltage Out
Current Loop
0xCAAA
~VSS
>20mA
0xCF0F
0xCE38
0xCCCC
0xC1C7
0xC555
0xC333
~VSS
~VSS
~VSS
~VSS
~VSS
~VSS
>20mA
>20mA
>20mA
>20mA
>20mA
>20mA
Sensor
Connection
Common
Mode Voltage
out of limits
0xCFCF
2’b10 ||
V
IN_CM
/2
~VDDA
~VDDA
<4mA
<4mA
V
IN_CM
… Measured Common Mode Voltage
Table 1:
Error Codes
Copyright © 2007, ZMD AG, Rev. 0.82, 2007-01-26,
5/46
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior
written consent of the copyright owner. The Information furnished in this publication is preliminary and subject to changes without notice.
京公网安备 11010802033920号
EEWORLD
