MCP98243 Microchip Technology Inc., MCP98243 Datasheet - Page 13

• Manufacturer Part Number: MCP98243
• Description: Memory Module Temperature Sensor W/ Eeprom For Spd
• Manufacturer: Microchip Technology Inc.

4.0
4.1
The MCP98243 serial clock input (SCL) and the
bidirectional serial data line (SDA) form a 2-wire
bidirectional
communication port (refer to the Input/Output Pin DC
Characteristics (Note 1) Table and Sensor And
EEPROM Serial Interface Timing Specifications
Table).
The following bus protocol has been defined:
TABLE 4-1:
4.1.1
Data transfers are initiated by a Start condition
(START), followed by a 7-bit device address and a
read/write bit. An Acknowledge (ACK) from the slave
confirms the reception of each byte. Each access must
be terminated by a Stop condition (STOP).
Repeated communication is initiated after t
© 2009 Microchip Technology Inc.
Master
Slave
Transmitter Device sending data to the bus.
Receiver
START
STOP
Read/Write A read or write to the MCP98243
ACK
NAK
Busy
Not Busy
Data Valid
Term
SERIAL COMMUNICATION
2-Wire Standard Mode I
Protocol-Compatible Interface
DATA TRANSFER
The device that controls the serial bus,
typically a microcontroller.
The device addressed by the master,
such as the MCP98243.
Device receiving data from the bus.
A unique signal from master to initiate
serial interface with a slave.
A unique signal from the master to
terminate serial interface from a slave.
registers.
A receiver Acknowledges (ACK) the
reception of each byte by polling the
bus.
A receiver Not-Acknowledges (NAK) or
releases the bus to show End-of-Data
(EOD).
Communication is not possible
because the bus is in use.
The bus is in the idle state, both SDA
and SCL remain high.
SDA must remain stable before SCL
becomes high in order for a data bit to
be considered valid. During normal
data transfers, SDA only changes state
while SCL is low.
Standard
MCP98243 SERIAL BUS
PROTOCOL DESCRIPTIONS
Description
mode
I
2
C
2
C™
B-FREE
compatible
.
This device does not support sequential register read/
write. Each register needs to be addressed using the
Register Pointer.
This device supports the Receive Protocol. The
register can be specified using the pointer for the initial
read. Each repeated read or receive begins with a Start
condition and address byte. The MCP98243 retains the
previously selected register. Therefore, it outputs data
from the previously-specified register (repeated pointer
specification is not necessary).
4.1.2
The bus is controlled by a master device (typically a
microcontroller) that controls the bus access and
generates the Start and Stop conditions. The
MCP98243 is a slave device and does not control other
devices in the bus. Both master and slave devices can
operate as either transmitter or receiver. However, the
master device determines which mode is activated.
4.1.3
A high-to-low transition of the SDA line (while SCL is
high) is the Start condition. All data transfers must be
preceded by a Start condition from the master. A low-
to-high transition of the SDA line (while SCL is high)
signifies a Stop condition.
If a Start or Stop condition is introduced during data
transmission, the MCP98243 releases the bus. All data
transfers are ended by a Stop condition from the mas-
ter.
4.1.4
Following the Start condition, the host must transmit an
8-bit address byte to the MCP98243. The address for
the
‘0011,A2,A1,A0’ in binary, where the A2, A1 and A0
bits are set externally by connecting the corresponding
pins to V
ted in the serial bit stream must match the selected
address for the MCP98243 to respond with an ACK. Bit
8 in the address byte is a read/write bit. Setting this bit
to ‘1’ commands a read operation, while ‘0’ commands
a write operation (see
FIGURE 4-1:
SDA
SCL
Start
MCP98243
DD
MASTER/SLAVE
START/STOP CONDITION
ADDRESS BYTE
‘1’ or GND ‘0’. The 7-bit address transmit-
1 2 3
0 0
Address
Code
1 1 A2 A1 A0
Figure
Address Byte
Device Addressing.
Temperature
4 5
MCP98243
Address
Slave
4-1).
6
MCP98243 Response
7
R/W
DS22153A-page 13
8
A
C
K
9
Sensor
is