DS2422 Maxim, DS2422 Datasheet - Page 14

• Manufacturer Part Number: DS2422
• Description: The DS2422 temperature/data logger combines the core functions of a fully featured data logger in a single chip
• Manufacturer: Maxim

Temperature Alarm Threshold Examples
SERIAL DATA INPUT
In addition to temperature, the DS2422 can log 8-bit or 16-bit digital information that it receives through its serial
interface. This interface is designed to directly connect to ADCs such as the MAX1086 or other circuits that use the
same interface timing. The general timing of the serial interface is shown in Figure 9. All timing is derived from an
on-chip ring oscillator, which generates the CLK signal. The CNVST signal is intended to start an analog-to-digital
conversion. After the conversion is completed, the SCLK signal becomes active and on its rising edge clocks the
digital value into the DS2422. The PUMP_ONZ signal can activate a MAX619 charge pump to convert the 3V
battery voltage of the DS2422 into 5V, for example, to power additional circuitry.
Figure 9A. Serial Interface Timing
Figure 9B. Serial Interface Setup and Hold Timing
The serial interface becomes active whenever the DS2422 executes a Forced Conversion command (see
Memory/Control Function Commands) or during a mission, if the device is set up to log data from its serial
interface. Regardless of its setup, the DS2422 always reads 16 bits from its serial input. The 16-bit result of the
latest serial reading is found at address 020Eh (low byte) and 020Fh (high byte). The first bit read through the
serial interface is always found as B15 at address 020Fh. If an ADC generates less than 16 bits, the internal weak
pulldown of the SDATA pin makes the missing bits read zero.
Latest Serial Data Reading Result Register Bitmap
During a mission, if data logging from the serial input is enabled, the HIGH byte (B15 to B8) is always recorded.
The LOW byte (B7 to B0) is only recorded if the DS2422 is set up for 16-bit logging of serial input data.
020Eh
020Fh
ADDR
PUMP_ONZ
(°C)
-10.0
25.5
CNVST
SDATA
SDATA
SCLK
SCLK
CLK
B15
B7
b7
hex
t
3Eh
85h
RING
TALM
t
SDS
B14
decimal
Data
Valid
B6
t
b6
SP
t
SDH
133
62
B13
B5
b5
t
CPW
B12
B4
b4
t
SCH
B11
B3
14 of 49
b3
B10
B2
b2
B15 B14 B13 B12 b4 B3 B2 B1 B0
t
SCP
B1
B9
b1
B0
B8
b0
HIGH
LOW