DS1923-F5# Maxim Integrated Products, DS1923-F5# Datasheet - Page 35

• Manufacturer Part Number: DS1923-F5#
• Description: IBUTTON TEMP/HUMIDITY LOGGER F5
• Manufacturer: Maxim Integrated Products
• Series: iButton®r

Specifications of DS1923-F5#

• Rohs Information: IButton RoHS Compliance Plan
• Memory Size: 512B
• Memory Type: NVSRAM (Non-Volatile SRAM)
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption

While a mission is in progress or while the device is
waiting for a temperature alarm to start a mission, peri-
odically a temperature and/or humidity sample is taken
and logged. This “internal activity” has priority over
1-Wire communication. As a consequence, device-spe-
cific commands (excluding ROM function commands
and 1-Wire reset) do not perform properly when internal
and “external” activities interfere with each other. Not
affected are the commands Start Mission, Forced
Conversion, and Clear Memory, because they are not
applicable while a mission is in progress or while the
Table 5. Memory Access Conflicts and Solutions
Write Scratchpad
Read Scratchpad
Copy Scratchpad
Read Memory with
CRC
Stop Mission
COMMAND
Hygrochron Temperature/Humidity Logger
Memory Access Conflicts
______________________________________________________________________________________
The CRC-16 at the end of the command flow reads
FFFFh.
The data read changes to FFh bytes or all bytes
received are FFh, including the CRC at the end of
the command flow.
The device behaves as if the authorization code or
password was not valid or as if the copy function
would not end.
The data read changes to all FFh bytes or all bytes
received are FFh, including the CRC at the end of
the command flow, despite a valid password.
The General Status register at address 0215h reads
FFh or the MIP bit is 1 while bits 0, 2, and 5 are 0.
INDICATION OF INTERFERENCE
iButton with 8KB Data-Log Memory
device is waiting for a temperature alarm. Table 5
explains how the remaining five commands are affect-
ed by internal activity, how to detect this interference,
and how to work around it.
The interference is more likely to be seen with a high-
sample rate (one sample every second) and with high-
resolution logging, which can last up to 666ms when
both temperature and humidity are recorded. With
lower sample rates, interference may hardly be visible
at all. In any case, when writing driver software it is
important to know about the possibility of interference
and to take measures to work around it.
Wait 0.5s, 1-Wire reset, address the device, repeat
Write Scratchpad with the same data, and check the
validity of the CRC-16 at the end of the command
flow. Alternatively, use Read Scratchpad to verify
data integrity.
Wait 0.5s, 1-Wire reset, address the device, repeat
Read Scratchpad, and check the validity of the
CRC-16 at the end of the command flow.
Wait 0.5s, 1-Wire reset, address the device, issue
Read Scratchpad, and check the AA bit of the E/S
byte. If the AA bit is set, Copy Scratchpad was
successful.
Wait 0.5s, 1-Wire reset, address the device, repeat
Read Memory with CRC, and check the validity of
the CRC-16 at the end of the memory page.
Wait 0.5s, 1-Wire reset, address the device, and
repeat Stop Mission. Perform a 1-Wire reset, address
the device, read the General Status register at
address 0215h, and check the MIP bit. If the MIP bit
is 0, Stop Mission was successful.
SOLUTION
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