Datasheet

MCP9843/98243
DS22153C-page 14 © 2009 Microchip Technology Inc.
4.1.5 DATA VALID
After the Start condition, each bit of data in
transmission needs to be settled for a time specified by
t
SU-DATA
before SCL toggles from low-to-high (see
“Sensor And EEPROM Serial Interface Timing
Specifications” on Page 5).
4.1.6 ACKNOWLEDGE (ACK/NAK)
Each receiving device, when addressed, is obliged to
generate an ACK bit after the reception of each byte.
The master device must generate an extra clock pulse
for ACK to be recognized.
The acknowledging device pulls down the SDA line for
t
SU-DATA
before the low-to-high transition of SCL from
the master. SDA also needs to remain pulled down for
t
H-DATA
after a high-to-low transition of SCL.
During read, the master must signal an End-of-Data
(EOD) to the slave by not generating an ACK bit (NAK)
once the last bit has been clocked out of the slave. In
this case, the slave will leave the data line released to
enable the master to generate the Stop condition.
4.1.7 TIME OUT (MCP9843/98243,
SENSOR ONLY)
If the SCL stays low or high for time specified by t
OUT
,
the MCP9843/98243 temperature sensor resets the
serial interface. This dictates the minimum clock speed
as specified in the specification. However, the
EEPROM does not reset the serial interface.
Therefore, the master can hold the clock indefinitely to
process data from the EEPROM.