LFEBS12UB Freescale Semiconductor, LFEBS12UB Datasheet - Page 597

• Manufacturer Part Number: LFEBS12UB
• Description: KIT STUDENT LEARNING S12 DG128
• Manufacturer: Freescale Semiconductor

Specifications of LFEBS12UB

• Architecture: 8/16-bit
• Code Gen Tools Included: Code Warrior
• Silicon Manufacturer: Freescale
• Core Architecture: S12
• Core Sub-architecture: S12
• Silicon Core Number: MC9S12
• Silicon Family Name: S12D
• Kit Contents: HCS12 DG128 Learning Kit
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

15.4.1.2
The first byte of data transfer immediately after the START signal is the slave address transmitted by the
master. This is a seven-bit calling address followed by a R/W bit. The R/W bit tells the slave the desired
direction of data transfer.
If the calling address is 10-bit, another byte is followed by the first byte.Only the slave with a calling
address that matches the one transmitted by the master will respond by sending back an acknowledge bit.
This is done by pulling the SDA low at the 9th clock (see
No two slaves in the system may have the same address. If the IIC bus is master, it must not transmit an
address that is equal to its own slave address. The IIC bus cannot be master and slave at the same
time.However, if arbitration is lost during an address cycle the IIC bus will revert to slave mode and operate
correctly even if it is being addressed by another master.
15.4.1.3
As soon as successful slave addressing is achieved, the data transfer can proceed byte-by-byte in a
direction specified by the R/W bit sent by the calling master
All transfers that come after an address cycle are referred to as data transfers, even if they carry sub-address
information for the slave device.
Each data byte is 8 bits long. Data may be changed only while SCL is low and must be held stable while
SCL is high as shown in
transferred first. Each data byte has to be followed by an acknowledge bit, which is signalled from the
receiving device by pulling the SDA low at the ninth clock. So one complete data byte transfer needs nine
clock pulses.
If the slave receiver does not acknowledge the master, the SDA line must be left high by the slave. The
master can then generate a stop signal to abort the data transfer or a start signal (repeated start) to
commence a new calling.
If the master receiver does not acknowledge the slave transmitter after a byte transmission, it means 'end
of data' to the slave, so the slave releases the SDA line for the master to generate STOP or START
signal.Note in order to release the bus correctly,after no-acknowledge to the master,the slave must be
immediately switched to receiver and a following dummy reading of the IBDR is necessary.
15.4.1.4
The master can terminate the communication by generating a STOP signal to free the bus. However, the
master may generate a START signal followed by a calling command without generating a STOP signal
first. This is called repeated START. A STOP signal is defined as a low-to-high transition of SDA while
SCL at logical 1 (see
The master can generate a STOP even if the slave has generated an acknowledge at which point the slave
must release the bus.
Freescale Semiconductor
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indicated here currently are not available from Freescale for import or sale in the United States prior to September 2010
1 = Read transfer, the slave transmits data to the master.
0 = Write transfer, the master transmits data to the slave.
Slave Address Transmission
Data Transfer
STOP Signal
Figure
Figure
15-10).
MC9S12XE-Family Reference Manual Rev. 1.23
15-10. There is one clock pulse on SCL for each data bit, the MSB being
Chapter 15 Inter-Integrated Circuit (IICV3) Block Description
Figure
15-10).
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