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MS563702BA03-50

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
MS5637-02BA03
Low Voltage Barometric Pressure Sensor
SENSOR SOLUTIONS /// MS5637-02BA03
09/2015
Page 10
RESET SEQUENCE
The Reset sequence shall be sent once after power-on to make sure that the calibration PROM gets loaded into
the internal register. It can be also used to reset the device PROM from an unknown condition.
The reset can be sent at any time. In the event that there is not a successful power on reset this may be caused by
the SDA being blocked by the module in the acknowledge state. The only way to get the MS5637 to function is to
send several SCLs followed by a reset sequence or to repeat power on reset.
Figure 5: I
2
C Reset Command
PROM READ SEQUENCE
The read command for PROM shall be executed once after reset by the user to read the content of the calibration
PROM and to calculate the calibration coefficients. There are in total 7 addresses resulting in a total memory of 112
bit. Addresses contains factory data and the setup, calibration coefficients, the serial code and CRC. The command
sequence is 8 bits long with a 16 bit result which is clocked with the MSB first. The PROM Read command consists
of two parts. First command sets up the system into PROM read mode. The second part gets the data from the
system.
Figure 6: I
2
C Command to read memory address= 011
Figure 7: I
2
C answer from MS5637
CONVERSION SEQUENCE
The conversion command is used to initiate uncompensated pressure (D1) or uncompensated temperature (D2)
conversion. After the conversion, using ADC read command the result is clocked out with the MSB first. If the
conversion is not executed before the ADC read command, or the ADC read command is repeated, it will give 0 as
the output result. If the ADC read command is sent during conversion the result will be 0, the conversion will not
stop and the final result will be wrong. Conversion sequence sent during the already started conversion process will
yield incorrect result as well. A conversion can be started by sending the command to MS5637. When command is
sent to the system it stays busy until conversion is done. When conversion is finished the data can be accessed by
sending a Read command, when an acknowledge is sent from the MS5637, 24 SCL cycles may be sent to receive
all result bits. Every 8 bits the system waits for an acknowledge signal.
1 1 1 0 1 1 0 0 0 0 0 0 1 1 1 1 0 0
S W A A P
From Master
S = Start Condition
W = Write A = Acknowledge
From Slave P = Stop Condition R = Read
N = Not Acknowledge
cmd byte
Device Address
Device Address
command
1 1 1 0 1 1 0 0 0 1 0 1 0 0 1 1 0 0
S W A A P
From Master
S = Start Condition
W = Write A = Acknowledge
From Slave P = Stop Condition R = Read
N = Not Acknowledge
Device Address
Device Address
cmd byte
command
1 1 1 0 1 1 0 1 0 X X X X X X X X 0 X X X X X X X X 0
S R A A N P
From Master
S = Start Condition
W = Write A = Acknowledge
From Slave P = Stop Condition R = Read N = Not Acknowledage
Memory bit 7 - 0
Device Address
Device Address
Memory bit 15 - 8
data
data
MS5637-02BA03
Low Voltage Barometric Pressure Sensor
SENSOR SOLUTIONS /// MS5637-02BA03
09/2015
Page 11
Figure 8: I
2
C command to initiate a pressure conversion (OSR=4096, typ=D1)
Figure 9: I
2
C ADC read sequence
Figure 10: I
2
C answer from MS5637
1 1 1 0 1 1 0 0 0 0 1 0 0 1 0 0 0 0
S W A A P
From Master
S = Start Condition
W = Write A = Acknowledge
From Slave P = Stop Condition R = Read
N = Not Acknowledge
cmd byte
Device Address
Device Address
command
1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0
S W A A P
From Master
S = Start Condition
W = Write A = Acknowledge
From Slave P = Stop Condition R = Read
N = Not Acknowledge
Device Address
Device Address
cmd byte
command
1
1
1
0
1
1
0
1
0
X
X
X
X
X
X
X
X
0
X
X
X
X
X
X
X
X
0
X
X
X
X
X
X
X
X
0
S
R
A
A
A
N
P
From Master
S = Start Condition
W = Write
A = Acknowledge
From Slave
P = Stop Condition
R = Read
N = Not Acknowledge
Data 7 - 0
Data 15 - 8
Device Address
Device Address
data
data
Data 23-16
data
MS5637-02BA03
Low Voltage Barometric Pressure Sensor
SENSOR SOLUTIONS /// MS5637-02BA03
09/2015
Page 12
CYCLIC REDUNDANCY CHECK (CRC)
MS5637 contains a PROM memory with 112-Bit. A 4-bit CRC has been implemented to check the data validity in
memory. The C code example below describes the CRC calculation which is stored on DB12 to DB15 in the first
PROM word.
A
d
d
D
B
1
5
D
B
1
4
D
B
1
3
D
B
1
2
D
B
1
1
D
B
1
0
D
B
9
D
B
8
D
B
7
D
B
6
D
B
5
D
B
4
D
B
3
D
B
2
D
B
1
D
B
0
0
CRC
Factory defined
1
C1
2
C2
3
C3
4
C4
5
C5
6
C6
Figure 11: Memory PROM mapping
C Code example for CRC-4 calculation:
unsigned char crc4(unsigned int n_prom[]) // n_prom defined as 8x unsigned int (n_prom[8])
{
int cnt; // simple counter
unsigned int n_rem=0; // crc reminder
unsigned char n_bit;
n_prom[0]=((n_prom[0]) & 0x0FFF); // CRC byte is replaced by 0
n_prom[7]=0; // Subsidiary value, set to 0
for (cnt = 0; cnt < 16; cnt++) // operation is performed on bytes
{ // choose LSB or MSB
if (cnt%2==1) n_rem ^= (unsigned short) ((n_prom[cnt>>1]) & 0x00FF);
else n_rem ^= (unsigned short) (n_prom[cnt>>1]>>8);
for (n_bit = 8; n_bit > 0; n_bit--)
{
if (n_rem & (0x8000)) n_rem = (n_rem << 1) ^ 0x3000;
else n_rem = (n_rem << 1);
}
}
n_rem= ((n_rem >> 12) & 0x000F); // final 4-bit reminder is CRC code
return (n_rem ^ 0x00);
}
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

MS563702BA03-50

Mfr. #:
Buy MS563702BA03-50
Manufacturer:
TE Connectivity / Measurement Specialties
Description:
Board Mount Pressure Sensors Low Volt Barometric Pressure Sensor
Lifecycle:
New from this manufacturer.
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