DS1921H/Z Maxim Integrated Products, DS1921H/Z Datasheet - Page 10

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

Status Register
The Status Register holds device status information and alarm flags. The register is located at address
214h. Writing to this register will not necessarily end a mission.
Status Register Bitmap
The functional assignments of the individual bits are explained in the table below. The bits MIP, TLF,
THF and THF, can only be written to 0. All other bits are read-only. Bit 3 has no function.
Status Register Details
TCB: Temperature Core
Busy
MEMCLR: Memory
Cleared
MIP: Mission in Progress
SIP: Sample in Progress
TLF: Temperature Low
Flag
THF: Temperature High
Flag
TAF: Timer Alarm Flag
ADDR
0214h
BIT DESCRIPTION
TCB
b7
MEMCLR
b6
BIT(S)
MIP
b7
b6
b5
b4
b2
b1
b0
b5
If this bit reads 0 the DS1921H/Z is currently performing a temperature
conversion, either self-initiated because of a mission being in progress
or initiated by a command when a mission is not in progress. The TCB
bit goes low just before a conversion starts and returns to high just after
the result is latched into the readout register at address 0211h.
If this bit reads 1, the memory pages 17 and higher (alarm time
stamps/durations, temperature histogram, excluding datalog memory),
as well as the Mission Time Stamp, Mission Samples Counter, Mission
Start Delay and Sample Rate have been cleared to 0 from executing a
Clear Memory function command. The MEMCLR bit will return to 0 as
soon as writing a non-0 value to the Sample Rate Register starts a new
mission, provided that the EM bit is also 0. The memory has to be
cleared in order for a mission to start.
If this bit reads 1 the DS1921H/Z has been set up for a mission and this
mission is still in progress. A mission is started if the EM bit of the
Control Register (address 20Eh) is 0 and a non-zero value is written to
the Sample Rate Register, address 20Dh. The MIP bit returns from logic
1 to logic 0 when a mission is ended. A mission will end with the first
write attempt (Copy Scratchpad command) to any register in the
address range of 200h to 213h. Alternatively, a mission can be ended by
directly writing to the Status Register and setting the MIP bit to 0. The
MIP bit cannot be set to 1 by writing to the status register.
If this bit reads 1 the DS1921H/Z is currently performing a temperature
conversion as part of a mission in progress. The SIP bit will change from
0 to 1 approximately 250ms before the actual temperature conversion
begins allowing the circuitry of the chip to wake-up. A temperature
conversion including a wake-up phase takes maximum 875ms. During
this time read accesses to the memory pages 17 and higher are
permissible but may reveal invalid data.
Logic 1 in the Temperature Low Flag bit indicates that a temperature
measurement during a mission revealed a temperature equal to or lower
than the value in the Temperature Low Threshold Register. The
Temperature Low Flag can be cleared at any time by writing this bit to 0.
Logic 1 in the Temperature High Flag bit indicates that a temperature
measurement during a mission revealed a temperature equal to or
higher than the value in the Temperature High Threshold Register.
The Temperature High Flag can be cleared at any time by writing this bit
to 0.
If this bit reads 1, a RTC alarm has occurred (see section
TIMEKEEPING for details). The Timer Alarm Flag can be cleared at any
time by writing this bit to logic 0. Since the timer alarm cannot be
disabled, the TAF flag usually reads 1 during a mission.
SIP
b4
b3
10 of 40
0
TLF
b2
DEFINITION
THF
b1
TAF
b0