DS1925 datasheet(42/46 Pages) MAXIM

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Mission Example: Prepare

and Start a New Mission

Assumption: The previous mission has been ended by

using the XPC Stop Mission command. Passwords are

not enabled. The device is a DS1925.

Starting a mission requires four steps:

Step 1: Clear the data of the previous mission.

Step 2: Write the setup data to register page 1.

Step 3: Start the mission.

Mission Example: Step 1

Clear the previous mission. With only a single device con-

nected to the bus master, the Step 1 communication looks

like Table 27.

Mission Example: Step 2

During the setup, the device needs to learn the following

information:

● Time and Date

● Sample Rate

● Alarm Thresholds

● Alarm Controls (Response to Conditional Search)

● General Mission Parameters (e.g., channels to log

and logging format, rollover, start mode)

● Mission Start Delay

Table 28 shows the data that sets up the DS1925 for a

mission that logs temperature using 11-bit format. Such a

mission could last up to 435 days until the 122KB data-log

memory is full. With only a single device connected to the

bus master, the Step 2 communication looks like Table 29.

Mission Example: Step 3

Start the new mission. With only a single device con-

nected to the bus master, the communication of Step 3

looks like Table 29. If Step 3 is successful, the MIP bit in

the General Status register is 1, the MEMCLR bit is be 0,

and the mission start delay counts down.

Table 27. Clear the Previous Mission Communication

DS1925

iButton High-Capacity Temperature Logger

with 122KB Data-Log Memory

www.maximintegrated.com

Maxim Integrated │ 42

MASTER MODE

DATA (LSB FIRST)

COMMENTS

(Reset)

Reset pulse

(Presence)

Presence pulse

CCh

Issue “Skip ROM” command

66h

Issue “XPC Command” command

0Ah

Issue length byte

96h

Issue “XPC Clear Memory” sub-command

01h

Parameter indicating “log” memory

<8 FFh bytes>

Send dummy password

<2 byte CRC16>

Read CRC of preceding bytes

FFh

Send release byte

Strong pullup and delay to perform memory clear tCML

(Repeat Byte)

Read repeat byte to indicate success

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