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Fujitsu Semiconductor (Shanghai) Co., Ltd.
Application Note
MCU-AN-500034-E-11
F²MC-8FX FAMILY
8-BIT MICROCONTROLLER
MB95200 SERIES
2
I C SW REALIZATION
USING GPIO
APPLICATION NOTE
I2C SW Realization Using GPIO V 1.1
Revision History
Revision History
Date
2009-02-04
2009-03-24
Author
Folix
Folix
Change of Records
V1.0, First draft
V1.1, Modify the format.
This manual contains 25 pages.
1.
The products described in this manual and the specifications thereof may be changed without prior notice.
To obtain up-to-date information and/or specifications, contact your Fujitsu sales representative or Fujitsu
authorized dealer.
2.
Fujitsu will not be liable for infringement of copyright, industrial property right, or other rights of a third party
caused by the use of information or drawings described in this manual.
3.
The contents of this manual may not be transferred or copied without the express permission of Fujitsu.
4.
The products contained in this manual are not intended for use with equipment which require extremely
high reliability such as aerospace equipment, undersea repeaters, nuclear control systems or medical
equipment for life support.
5.
Some of the products described in this manual may be strategic materials (or special technology) as
defined by the Foreign Exchange and Foreign Trade Control Law. In such cases, the products or portions
thereof must not be exported without permission as defined under the law.
© 2008 Fujitsu Semiconductor (Shanghai) Co., Ltd.
MCU-AN-500034-E-11- Page 2
I2C SW Realization Using GPIO V 1.1
CONTENTS
CONTENTS
Revision History .............................................................................................................. 2 CONTENTS .................................................................................................................... 3 1 Introduction .............................................................................................................. 4 2 Overview of I2C ........................................................................................................ 5 2.1 Background ................................................................................................... 5 2.2 Protocol ......................................................................................................... 6 2.2.1 START Condition and STOP Condition ................................................. 6 2.2.2 Byte Format ............................................................................................ 7 2.2.3 Acknowledge .......................................................................................... 8 2.2.4 A Complete Data Transfer.................................................................... 10 3 2
I C Driver ................................................................................................................ 11 3.1 Peripheral Usage ........................................................................................ 11 3.2 Driver Code ................................................................................................. 12 3.2.1 General Definition................................................................................. 12 3.2.2 I2C Routines ......................................................................................... 13 4 Typical Application ................................................................................................. 19 4.1 HW Design .................................................................................................. 19 4.2 Sample Code .............................................................................................. 20 4.3 I2C Wave (E2PROM Read and Write Wave) .............................................. 22 4.3.1 Write Wave-->Rom_Write (0xA0,0X11,0X35) ...................................... 22 4.3.2 Read Wave-->Rom_Read (0xA1,0X11) ............................................... 22 5 Notes on Items ....................................................................................................... 23 6 More Information .................................................................................................... 24 7 Appendix ................................................................................................................ 25 MCU-AN-500034-E-11- Page 3
I2C SW Realization Using GPIO V 1.1
Chapter 1 Introduction
1 Introduction
In this document, we will introduce how to use the GPIO to realize I2C function on the
MB95200 series.
MCU-AN-500034-E-11- Page 4
I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
2 Overview of I2C
2.1 Background
In consumer electronics, telecommunications and industrial electronics, there are
often many similarities among different designs. The following blocks are nearly
included in every system.
Some intelligent control, usually a single-chip microcontroller
General-purpose circuits like LCD drivers, remote I/O ports, RAM, E2PROM, or data
converters
Application-oriented circuits, such as digital tuning and signal processing circuits for
radio and video systems, or DTMF generators for telephones with tone dialing
In these blocks listed above, the control and communication among different chips
may be performed. To maximize hardware efficiency and circuit simplicity, Philips
developed a simple bi-directional 2-wire bus for efficient inter-IC control. This bus is
called "inter IC" or "I2C-bus".
Now, Philips’ IC includes more than 150 CMOS and bipolar I2C-bus compatible used
to perform corresponding functions mentioned above. All I2C-bus compatible with
devices build in an on-chip interface which supports them to communicate directly
each other via I2C-bus. This concept has solved many problems related to interface
when designing digital control circuits.
Here are some features of I2C-bus:
Only two lines are required: a serial data line (SDA) and a serial clock line (SCL).
For each device connected to the bus, only an independent address and a simple
master/slaver relationship are needed. The master can operate as a transmitter or a
receiver.
A true multi-master mode can be realized only by bus arbitration and collision
detection.
In 8-bit bi-directional serial transfer, data transfer rate can be up to 100 Kbit/s in
standard-mode and up to 400 Kbit/s in fast-mode and up to 3.4 Mbit/s in high speed
mode.
On-chip bus filtering function can preserve the integrity of communication data on the
bus.
The number of ICs that can be connected to the same bus is limited only by a
maximum bus capacitance of 400 pF.
MCU-AN-500034-E-11- Page 5
I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
2.2 Protocol
2.2.1 START Condition and STOP Condition
In I2C communication, START (S) condition and STOP (P) condition should be set
respectively.
SDA line is changed from HIGH to LOW while SCL is HIGH; this case is defined as a
START condition.
SCL is changed from LOW to HIGH while SCL is HIGH; this case is defined as a
STOP condition.
The START condition and the STOP condition are always generated by the master.
The bus is busy when the START condition is generated and is free when the STOP
condition is generated.
The bus also remains busy if a repeated START (Sr) is generated instead of a STOP
condition. In the case above, the function of the START (S) condition and the
repeated START (Sr) condition are regarded as the same.
It is easy to detect the START condition and the STOP condition by devices
connected to the bus, if they build in necessary hardware interface. However, if the
controller does not have such interface, it must sample the SDA line at least twice per
clock period so that the master can recognise the START condition and the STOP
condition.
Figure 1 START Condition and STOP Condition
MCU-AN-500034-E-11- Page 6
I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
2.2.2 Byte Format
Each byte on the SDA line should be 8bits long. The number of bytes that can be
transferred at a time is arbitrary. Each byte should be followed by an acknowledge bit.
Data transfer starts from the most significant bit (MSB first). If the slaver can not
receive or transfer a complete byte data, for example, an internal interrupt processing,
SCL line should be set as LOW to force the master into a wait sate. Data transfer can
be performed until the slaver is ready for next byte data and releases SCL line.
In some cases, you can use a format different from I2C-bus format (for example,
CBUS compatible devices). A message which starts with such an address can be
terminated by generating a STOP condition, even during a byte transfer. In this case,
a no acknowledge is generated.
MCU-AN-500034-E-11- Page 7
I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
2.2.3 Acknowledge
An acknowledge is necessary for data transfer. The clock pulse related to
acknowledge is generated by the master. During the acknowlede clock pulse, the
transmitter releases the SDA line (HIGH), the receiver pulls down the SDA line and
always remains LOW during the HIGH period of the clock pulse. Please note that
setup time and hold time should also be considered.
Usually, a receiver which has been addressed generates an acknowledge every time
after a byte data is received. An exception is that the receiver accesses on CBUS
addressing and sends a message.
If a slaver can not recognise the slave address (for example, it is performing some
real-time function), the SDA line should be left HIGH by the slaver. In this case, the
master sholuld terminate data transfer by generating a STOP condition or start a new
transfer by generating a repeated START condition.
If a slave-receiver does not receive any byte data for some time after recognising the
slave address, the master must terminate data transfer again.
If the slaver generates a no acknowledge immediately after the first byte, the slaver
will set SDA as HIGH, so the master should generate a STOP condition or a repeated
START condition.
If the master-receiver also performs data transfer, it should send a no acknowlede to
the slave-transmitter when the slaver has sent the last data. The slave-transmitter
must release the SDA line so that the master can generate a STOP condition or a
repeated START condition.
Figure 2 Data Transfer on the I2C-bus
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I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
Figure 3 Acknowledge on the I2C-bus
MCU-AN-500034-E-11- Page 9
I2C SW Realization Using GPIO V 1.1
Chapter 2 Overview of I2C
2.2.4 A Complete Data Transfer
Data transfer format is shown in Figure.4 as below. A slave address is transferred
after the START condition (S) is generated. This address is 7 bits long followed by the
eighth bit which is a data direction bit (R/W) ("0": Write, ‘1’: Read). Data transfer is
always terminated by the STOP condition (P) generated by the master. However, if
the master still needs to perform data transfer on the bus, it can generate a repeated
START condition (Sr) and address another slaver without generating a STOP
condition first. This way above can be used for various read/write formats.
Figure 4 A Complete Data Transfer on the I2C-bus
MCU-AN-500034-E-11- Page 10
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
3 I2C Driver
3.1 Peripheral Usage
The MCU pins are used as below.
P62, used as SDA;
P63, used as SCL;
MCU-AN-500034-E-11- Page 11
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
3.2 Driver Code
3.2.1 General Definition
typedef unsigned char
typedef unsigned char
typedef signed
char
typedef unsigned int
typedef signed
int
typedef unsigned long
typedef signed
long
BOOLEAN;
INT8U;
INT8S;
INT16U;
INT16S;
INT32U;
INT32S;
#define BOOL
#define BYTE
#define UBYTE
#define WORD
#define UWORD
#define LONG
#define ULONG
#define UCHAR
#define UINT
#define DWORD
BOOLEAN
INT8U
INT8U
INT16U
INT16U
INT32S
INT32U
INT8U
INT16U
INT32U
#define TRUE
#define FALSE
#define SDA
#define SCL
/* Unsigned 8 bit quantity */
/* Signed
8 bit quantity */
/* Unsigned 16 bit quantity */
/* Signed
16 bit quantity */
/* Unsigned 32 bit quantity */
/* Signed
32 bit quantity */
1
0
PDR6_P62
PDR6_P63
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I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
3.2.2 I2C Routines
void I2C_BusInit()
Return
: None.
Parameters : None.
Description
: Initialize the I2C.
Example
:
I2C_BusInit ();
void I2C_BusInit()
{
DDR6_P62=1; //SDA-OUT
DDR6_P63=1; //SCL-OUT
PDR6_P62=0; //SDA-0
PDR6_P63=0; //SCL-0
}
void DelayUS(UINT nDly)
Return
: None.
Parameters :
nDly,delay US.
Description : Delay nDly on the I2C.
Example
:
DelayUS(3);
void DelayUS(UINT nDly)
{
for(;nDly>0;nDly--){}
}
Note: The clock loop varies depending on MCU, please change the ‘DelayUS()’
function to realize the s delay.
MCU-AN-500034-E-11- Page 13
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
void Start ()
Return
Parameters
Description
Example
Start ();
: None.
: None.
: Start I2C transfer.
:
void Start()
{
SCL=0;
SDA=1;
DDR6_P62=1; //SDA-OUT
DelayUS(2);
SCL=1;
DelayUS(2);
SDA=0;
DelayUS(2);
}
void Stop()
Return
Parameters
Description
Example
Stop ();
: None.
: None.
: Stop I2C transfer.
:
void Stop()
{
SCL=0;
SDA=0;
DDR6_P62=1; //SDA-OUT
DelayUS(2);
SCL=1;
DelayUS(2);
SDA=1;
DelayUS(2);
}
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I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
void SetAck()
Return
Parameters
Description
Example
SetAck ();
: None.
: None.
: Set an acknowledge on the I2C.
:
void SetAck()
{
SCL=0;
DelayUS(2);
SDA=0;
DDR6_P62=1; //SDA-OUT
DelayUS(2);
SCL=1;
DelayUS(2);
}
BOOL GetAck()
Return
: 0,failure 1,success.
Parameters : None.
Description : Get an acknowledge from the I2C.
Example
:
BOOL bAck;
bAck=GetAck ();
BOOL GetAck()
{
SCL=0;
DelayUS(2);
SDA=1;
DDR6_P62=0; //SDA-IN
SCL=1;
DelayUS(2);
return SDA? FALSE:TRUE;
}
MCU-AN-500034-E-11- Page 15
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
void NoAck()
Return
Parameters
Description
Example
NoAck ();
: None.
: None.
: Set a no acknowledge on the I2C.
:
void NoAck()
{
SCL=0;
DelayUS(2);
SDA=1;
DDR6_P62=1; //SDA-OUT
DelayUS(2);
SCL=1;
DelayUS(2);
}
MCU-AN-500034-E-11- Page 16
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
void Write8Bit(UCHAR uDat)
Return
: None.
Parameters :
uDat, 8-bit data.
Description : Write a 8-bit data on the I2C.
Example
:
Write8Bit (0x63);
void Write8Bit(UCHAR uDat)
{
UCHAR i;
SCL=0;
DDR6_P62=1; //SDA-OUT
for(i=8;i!=0;i--)
{
DelayUS(2);
SDA=(uDat&0x80)? 1:0;
DelayUS(2);
SCL=1;
DelayUS(2);
SCL=0;
uDat<<=1;
}
}
MCU-AN-500034-E-11- Page 17
I2C SW Realization Using GPIO V 1.1
Chapter 3 I2C Driver
UCHAR Read8Bit()
Return
: Data from the I2C.
Parameters : None.
Description : Read a 8-bit data from the I2C.
Example
:
UCHAR tmp;
tmp=Read8Bit ();
UCHAR Read8Bit()
{
UCHAR i;
UCHAR uRByte=0;
SCL=0;
SDA=1;
DDR6_P62=0; //SDA-IN
for(i=8;i!=0;i--)
{
DelayUS(2);
SCL=1;
DelayUS(2);
uRByte<<=1;
uRByte|=(UCHAR)(SDA);
SCL=0;
}
return uRByte;
}
MCU-AN-500034-E-11- Page 18
I2C SW Realization Using GPIO V 1.1
Chapter 4 Typical Application
4 Typical Application
4.1 HW Design
In this application, MB95F204K is used as MCU chip and E2PROM (AT24C08) is
used as the I2C device. The HW is designed as Figure.5.
Figure 5 Hardware Design
MCU-AN-500034-E-11- Page 19
I2C SW Realization Using GPIO V 1.1
Chapter 4 Typical Application
4.2 Sample Code
The codes are applied to AT24C08. Please refer to the AT24C08 manual for more
information. In the demo, the address for AT24C08 is set as 0xA0 and the baudrate is
set as 1 kbit/s.
BOOL Rom_Write(UBYTE romAddr,UBYTE datAddr,UBYTE data)
Return
: 0,failure 1,success.
Parameters :
romAddr,the AT24C08 address;
datAddr,the memory space address;
data, data written to the AT24C08.
Description : Write a data to the AT24C08 by I2C.
Example
:
BOOL bSuc;
bSuc=Rom_Write(0xA0,0x35,0x62);
BOOL Rom_Write(UBYTE romAddr,UBYTE datAddr,UBYTE data)
{
Start();
Write8Bit(romAddr&0xFE); //I2C write address
if(!GetAck())
return FALSE;
Write8Bit(datAddr);
if(!GetAck())
return FALSE;
Write8Bit(data);
if(!GetAck())
return FALSE;
Stop();
return TRUE;
}
MCU-AN-500034-E-11- Page 20
I2C SW Realization Using GPIO V 1.1
Chapter 4 Typical Application
UBYTE Rom_Read(UBYTE romAddr,UBYTE datAddr)
Return
: data from AT24C08.
Parameters
:
romAddr,the AT24C08 address;
datAddr,the memory space address;
Description
: Read a data from the AT24C08 by I2C.
Example
:
UBYTE tmp;
tmp=Rom_Read (0xA1,0x35);
UBYTE Rom_Read(UBYTE romAddr,UBYTE datAddr)
{
UBYTE value;
Start();
Write8Bit(romAddr&0xFE); //I2C write address
if(!GetAck())
return FALSE;
Write8Bit(datAddr);
if(!GetAck())
return FALSE;
Start();
Write8Bit(romAddr|0x01); //I2C read address
if(!GetAck())
return FALSE;
value=Read8Bit();
NoAck();
Stop();
return value;
}
MCU-AN-500034-E-11- Page 21
I2C SW Realization Using GPIO V 1.1
Chapter 1
4.3 I2C Wave (E2PROM Read and Write Wave)
4.3.1 Write Wave-->Rom_Write (0xA0,0X11,0X35)
Figure. 6 Write Wave
4.3.2 Read Wave-->Rom_Read (0xA1,0X11)
Figure 7 Read Wave
MCU-AN-500034-E-11- Page 22
I2C SW Realization Using GPIO V 1.1
Chapter 5 Notes on Items
5 Notes on Items
I2C address bit0 setting :
The bit0 is set as "1" in read mode and is set as "0" in write mode.
In the function “void DelayUS(UINT nDly)”, the ‘nDly’ is different from the other MCU.
Please set the ‘nDly’ according to MCU.
MCU-AN-500034-E-11- Page 23
I2C SW Realization Using GPIO V 1.1
Chapter 6 More Information
6 More Information
For more information on FUJITSU MB95200 products, please visit following websites:
English version:
http://www.fujitsu.com/cn/fsp/services/mcu/mb95/application_notes.html
Simplified Chinese Version:
http://www.fujitsu.com/cn/fss/services/mcu/mb95/application_notes.html
MCU-AN-500034-E-11- Page 24
I2C SW Realization Using GPIO V 1.1
Chapter 7 Appendix
7 Appendix
Figure 1 START Condition and STOP Condition ............................................................... 6 Figure 2 Data Transfer on the I2C-bus ................................................................................. 8 Figure 3 Acknowledge on the I2C-bus ................................................................................. 9 Figure 4 A Complete Data Transfer on the I2C-bus ......................................................... 10 Figure 5 Hardware Design ................................................................................................... 19 Figure. 6 Write Wave ............................................................................................................ 22 Figure 7 Read Wave ............................................................................................................. 22 MCU-AN-500034-E-11- Page 25
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