DS1921 datasheet(12/44 Pages) DALLAS

12 / 44 page

DS1921H/Z

12 of 44

Mission Samples Counter Register Map

ADDR

021Ah

Low Byte

021Bh

Center Byte

021Ch

High Byte

DEVICE SAMPLES COUNTER

The Device Samples Counter indicates how many temperature measurements have taken place since the

device was assembled at the factory. The value is stored as an unsigned 24-bit integer number. The

maximum number that can be represented in this format is 16777215, which is higher than the expected

lifetime of the DS1921H/Z iButton. This counter cannot be reset under software control.

Device Samples Counter Register Map

ADDR

021Dh

Low Byte

021Eh

Center Byte

021Fh

High Byte

TEMPERATURE LOGGING AND HISTOGRAM

Once setup for a mission, the DS1921H/Z logs the temperature measurements simultaneously byte after

byte in the datalog memory as well as in histogram form in the histogram memory. The datalog memory

is able to store 2048 temperature values measured at equidistant time points. The first temperature value

of a mission is written to address location 1000h of the datalog memory, the second value to address

location 1001h and so on. Knowing the starting time point (Mission Time Stamp), the interval between

temperature measurements, the Mission Samples Counter, and the rollover setting, one can reconstruct

the time and date of each measurement stored in the datalog.

There are two alternatives to the way the DS1921H/Z will behave after the 2048 bytes of datalog memory

is filled with data. With rollover disabled (RO = 0), the device will fill the datalog memory with the first

2048 mission samples. Additional mission samples are not logged in the datalog, but the histogram, and

temperature alarm memory continue to update. With rollover enabled (RO = 1), the datalog will wrap

around, and overwrite previous data starting at 1000h for the every 2049

th mission sample. In this mode

the device stores the last 2048 mission samples.

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.

DS1921 датащи(PDF) 12 Page - Dallas Semiconductor

DS1921 датащи(HTML) 12 Page - Dallas Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

датащи скачать

ссылки URL