tcn75 Microchip Technology Inc., tcn75 Datasheet - Page 8

• Manufacturer Part Number: tcn75
• Description: 2-wire Serial Temperature Sensor And Thermal Monitor
• Manufacturer: Microchip Technology Inc.

TCN75
4.0
When the appropriate bit is set in the configuration reg-
ister (CONFIG) the TCN75 enters its low-power Shut-
down mode (I
to-digital conversion process is halted. The TCN75’s
bus interface remains active and TEMP, T
T
SDA or SCL due to external bus activity may increase
the standby power consumption. If the TCN75 is in
Interrupt mode, the state of INT/CMPTR will be reset
upon entering Shutdown mode.
4.1
To lessen the probability of spurious activation of INT/
CMPTR the TCN75 may be programmed to filter out
transient events. This is done by programming the
desired value into the Fault Queue. Logic inside the
TCN75 will prevent the device from triggering INT/
CMPTR unless the programmed number of sequential
temperature-to-digital conversions yield the same
qualitative result. In other words, the value reported in
TEMP must remain above T
consecutive number of cycles programmed in the Fault
Queue. Up to a six-cycle “filter” may be selected. See
Section 5.0 “Register Set and Programmer’s
ModeL”, Register Set and Programmer’s Model.
4.2
The Serial Clock input (SCL) and bidirectional data port
(SDA) form a 2-wire bidirectional serial port for pro-
gramming and interrogating the TCN75. The following
table indicates TCN75 conventions that are used in this
bus scheme.
DS21490C-page 8
HYST
may be read from and written to. Transitions on
SHUTDOWN MODE
Fault Queue
Serial Port Operation
DD
= 1 μA, typical) and the temperature-
SET
or below T
HYST
SET
for the
, and
TABLE 4-1:
All transfers take place under control of a host, usually
a CPU or microcontroller, acting as the Master, which
provides the clock signal for all transfers. The TCN75
always operates as a Slave. This serial protocol is
illustrated in Figure 5-1. All data transfers have two
phases; and all bytes are transferred MSB first.
Accesses are initiated by a Start condition, followed by
a device address byte and one or more data bytes. The
device address byte includes a Read/Write selection
bit. Each access must be terminated by a Stop condi-
tion. A convention called Acknowledge (ACK) confirms
receipt of each byte. Note that SDA can change only
during periods when SCL is LOW (SDA changes while
SCL is HIGH are reserved for Start and Stop condi-
tions).
4.3
The TCN75 continuously monitors the SDA and SCL
lines for a Start condition (a HIGH-to-LOW transition of
SDA while SCL is HIGH), and will not respond until this
condition is met.
Transmitter
NOT Busy
Data Valid
Receiver
Master
Slave
Term
Start
Stop
ACK
Start Condition (Start)
The device sending data to the bus.
The device receiving data from the bus.
The device which controls the bus: initiating
transfers (Start), generating the clock, and
terminating transfers (Stop).
The device addressed by the master.
A unique condition signaling the beginning of
a transfer indicated by SDA falling (High –
Low) while SCL is high.
A unique condition signaling the end of a
transfer indicated by SDA rising (Low – High)
while SCL is high.
A Receiver acknowledges the receipt of each
byte with this unique condition. The Receiver
drives SDA low during SCL high of the ACK
clock-pulse. The Master provides the clock
pulse for the ACK cycle.
When the bus is idle, both SDA & SCL will
remain high.
The state of SDA must remain stable during
the High period of SCL in order for a data bit
to be considered valid. SDA only changes
state while SCL is low during normal data
transfers. (See Start and Stop conditions).
SERIAL BUS CONVENTIONS
© 2006 Microchip Technology Inc.
Explanation