DS1921H/Z Maxim Integrated Products, DS1921H/Z Datasheet - Page 12

• Manufacturer Part Number: DS1921H/Z
• Description: High Resolution Thermochron Ibutton Range H
• Manufacturer: Maxim Integrated Products

There are two alternatives to the way the DS1921H/Z will behave after the 2048 bytes of datalog memory
is filled with data. The user can program the device to either stop any further recording (disable rollover)
or overwrite the previously recorded data (enable rollover), one byte at a time, starting again at address
1000h for the 2049
21Ch) in conjunction with the sample rate and the Mission Time Stamp will then allow reconstructing the
time points of all values stored in the datalog memory. This gives the exact temperature history over time
for the latest 2048 measurements taken. All earlier measurements cannot be reconstructed. Regardless of
enabling the rollover, these values are included in the mission’s temperature histogram.
For the temperature histogram, the DS1921H/Z provides 64 bins that begin at memory address 0800h.
Each bin consists of a 16-bit, non-rolling-over binary counter that is incremented each time a temperature
value acquired during a mission falls into the range of the bin. The least significant byte of each bin is
stored at the lower address. Bin 0 begins at memory address 0800h, bin 1 at 0802h, and so on up to
087Eh for bin 63, as shown in Figure 7. The number of the bin to be updated after a temperature
conversion is determined by cutting off the two least significant bits of the binary temperature value. Out
of range values are range locked and counted as 00h or FFh.
HISTOGRAM BIN AND TEMPERATURE CROSS-REFERENCE Figure 7
Since each data bin is 2 bytes it can increment up to 65535 times. Additional measurements for a bin that
has already reached its maximum value will not be counted; the bin counter will remain at its maximum
value. With the fastest sample rate of one sample every minute, a 2-byte bin is sufficient for up to 45 days
if all temperature readings fall into the same bin.
TEMPERATURE
READING
FAh
FBh
FCh
FDh
FEh
F7h
F8h
F9h
FFh
00h
01h
02h
03h
04h
05h
06h
07h
08h
th
temperature value. The contents of the Mission Samples Counter (addresses 21Ah to
TEMP. EQUIV. IN
DS1921H
14.500
14.625
14.750
14.875
15.000
15.125
15.250
15.375
15.500
45.375
45.500
45.625
45.750
45.875
46.000
46.125
46.250
46.375
°C
TEMP. EQUIV. IN
DS1921Z
12 of 40
25.375
25.500
25.625
25.750
25.875
26.000
26.125
26.250
26.375
-5.500
-5.375
-5.250
-5.125
-5.000
-4.875
-4.750
-4.625
-4.500
°C
HISTOGRAM BIN
NUMBER
61
62
62
62
62
63
63
63
63
0
0
0
0
1
1
1
1
2
HISTOGRAM BIN
87Ch to 87Dh
87Ch to 87Dh
87Ch to 87Dh
87Ch to 87Dh
87Ah to 87Bh
87Eh to 87Fh
87Eh to 87Fh
87Eh to 87Fh
87Eh to 87Fh
800h to 801h
800h to 801h
800h to 801h
800h to 801h
802h to 803h
802h to 803h
802h to 803h
802h to 803h
804h to 805h
ADDRESS