MCF5272I2CUG, MCF5272 Soft I2C
Contents
1. this is handled within software 1 3 1 1 2 buffer The buffer argument points to the memory location of the read buffer Before calling any of the IC functions the user must define a read buffer The size of the buffer is dependent on the specific application implemented by the and therefore has no maximum size requirement 1 3 1 1 3 byte _count This parameter tells the i2c_read function how many bytes to read from the slave device Again there is no maximum value but there must be at least one byte read when calling the function If byte_count is set to 0 the MCF5272 will not properly terminate communication with the slave device since it will not be able to hold the acknowledge bit high after a byte transfer If this parameter is larger than the size of the read buffer data will be lost 1 3 1 1 4 freq This argument determines the transmission frequency for the read process Note that this value is passed as an integer value and is to be entered in increments of 1 For example when running from SDRAM with cache disabled on the M5272C3 evaluation board the value entered is close to its corresponding frequency in kHz 75 is about 75 kHz Since this calculation is based on a mathematical equation the frequency will have some margin of error MOTOROLA MCF5272 Soft IC User s Guide 4 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc 1 3 1 1 5 Read Status Byte The read function re2. C 2 1 1 Setting Up the MCF5272 Once the i2c h and i2c c files are incorporated into a project initializing C communication is very simple The following program sets up a read and write buffer before calling the C functions Once the transmission starts it sends the contents of the write buffer to the iPort followed by a read of the data provided by the iPort After the read it writes the data that was 9 MCF5272 Soft IC User s Guide MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc read back to the iPort It finishes by again sending the contents of the write buffer The following code is used for this procedure void main void uint8 read_buffer 12 uint8 write buffer 12 0xE3 0x56 OxC2 OxFE 0x00 OxFF 0x53 0xB1 Ox7C 0x42 OXF9 OxEE uint8 status 0x81 i2c_init Note The status is not being monitored in this example status i2c write 0x6E write buffer 12 75 status i2c read 0x6E read_buffer 12 75 status i2c write 0x6E read_buffer 12 75 status i2c write 0x6E write buffer 12 75 status i2c_ stop Figure 2 shows the information that the iPort device has logged iix Eile view Options Help Communication Events Slave Message Data Bytes 12 Available 12C Slave Message Received 0x0211 SRx 12 Bytes Received 12C Slave Message Received 0x0211 SRx 12 Bytes Received 12C Des
3. Freescale Semiconductor Inc Technical Data ale Ad Yd MOTOROLA Pr b MCF 5272I2CUG intelligence everywhere digi taldna Rev 0 3 2002 MCF5272 Soft PC User s Guide Eric Ocasio Paice To address customer needs Motorola has developed a set of C based software IC TECD Applications Inter IC functions for the ColdFire MCF5272 microprocessor implemented via general purpose I O These functions support master mode and transfers clocked up to 100 kHz The IC bus is a standard that was introduced by Philips Semiconductors Its straightforward concept and manufacturing simplicity has made it a widely recognized form of inter chip communication in embedded systems Common peripherals such as LCD drivers memory and keyboard interfaces can be I C compatible This document provides information about how to use the Soft IC functions and integrate them into a MCF5272 based system Specifically it describes the interface hardware software configuration and protocol and how to test the system This document discusses the following topics Topics Section I Interface Description 1 1 Software Functionality 1 2 Init Function 1 3 Read Function 1 4 Write Function 1 5 Stop Funtion 1 6 Calling Sequences 1 7 Hardware Interface Section II Functional Tests 2 1 Communication with iPort device 2 2 Alternative Interrupt Driven Implementation For M
4. Not Listed Motorola Literature Distribution P O Box 5405 Denver Colorado 80217 1 800 521 6274 or 480 768 2130 JAPAN Motorola Japan Ltd SPS Technical Information Center 3 20 1 Minami Azabu Minato ku Tokyo 106 8573 Japan 81 3 3440 3569 ASIA PACIFIC Motorola Semiconductors H K Ltd Silicon Harbour Centre 2 Dai King Street Tai Po Industrial Estate Tai Po N T Hong Kong 852 26668334 HOME PAGE http motorola com semiconductors MOTOROLA Information in this document is provided solely to enable system and software implementers to use Motorola products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Motorola reserves the right to make changes without further notice to any products herein Motorola makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Motorola assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incidental damages Typical parameters that may be provided in Motorola data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each cus
5. actored into the timer s reference value Once this has been addressed this method can achieve extremely precise clocking for the Soft PC Section Ill Conclusion This document has outlined how to use the Soft IC provided by Motorola This implementation is designed to be a simple solution for using IC hardware with the MCF5272 Section 2 2 discussed higher level implementation if there is any need for a more precise clocking mechanism It is important to understand that when developing the Soft IC the code was run out of SDRAM with the cache disabled on an M5272C3 evaluation board All documented performance frequency wise is based on these conditions Performance may differ if other configurations are used MOTOROLA MCF5272 Soft I2C User s Guide 12 For More Information On This Product Go to www freescale com 13 Freescale Semiconductor Inc THIS PAGE INTENTIONALLY LEFT BLANK MCF5272 Soft IC User s Guide For More Information On This Product Go to www freescale com MOTOROLA MOTOROLA Freescale Semiconductor Inc THIS PAGE INTENTIONALLY LEFT BLANK MCF5272 Soft I2C User s Guide For More Information On This Product Go to www freescale com 15 Freescale Semiconductor Inc THIS PAGE INTENTIONALLY LEFT BLANK MCF5272 Soft IC User s Guide For More Information On This Product Go to www freescale com MOTOROLA Freescale Semiconductor Inc HOW TO REACH US USA EUROPE Locations
6. d output mode in the data direction register leaves the line high or pulls it low When the DDR is cleared to O input mode the SDA SCL remains high When the DDR is set to 1 output mode the SDA SCL is pulled low since the data register has a 0 written to it The SDA and SCL macros shown below are based on this concept define SDA high MCF5272_GPIO_PADDR amp 0xFBFF define SDA low MCF5272 GPIO PADDR 0x0400 define SCL high MCF5272 GPIO PADDR amp 0xFDFF define SCL low MCF5272 GPIO PADDR 0x0200 Section Il Functional Test This section details successful IC communication between the Soft IC and a device with IC capable hardware This conformance testing was performed using a M5272C3 evaluation board and an iPort MIIC 201V IC tool see Table 2 for details about this device All software was written using the Metrowerks CodeWarrior IDE for ColdFire and was run from SDRAM with the cache disabled 2 1 The iPort Device The easiest way to test the Soft IC is to use a device that provides a simple PC graphical user interface and does not require extensive programming The iPort is such a device It connects through the serial port of a machine and provides a simple user interface that allows the user to select the various parameters for an IC transfer Another key feature of the iPort is that it requires absolutely no programming This is the device that was used throughout the build and testing phases of the Soft I
7. e ISR has finished all operations for a 9 cycle transmission i2c_ write Initialize variables SCL_low oo i lt byte count isr_ parity 1 isr_count 0 isr_done 0 Set up timer registers TMR TER TRR TCN Put first bit on SDA line Wait for SCL to be released by slave while isr_done 1 Wait for ISR to finish Update write buffer to point to next byte SDA_high SCL low return status The following is an example of the ISR _ i nterrupt__ timerX_handler void Clear Timer Event Register isr_parity 0 if isr_count 15 11 MCF5272 Soft IC User s Guide MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc SDA_high SCL high Update status byte depending on ACK signal isr_ parity 1 isr_count else Put data bit on SDA one bit at a time SCL_high isr_ parity 1 isr_count else if isr_count 16 SCL_low Turn off timer isr_ parity 0 isr_ done 1 else SCL_low Update any mask used to send data isr_ parity 0 isr_count This example shows how to use an ISR to do all of the work in sending the data and clock signals for an IC write procedure A similar procedure could be used to do the same thing for the i2c_read function It should be noted that there is some overhead involved with using an ISR such as the execution time of the code that would need to be measured and f
8. ead This function performs a standard IC read operation After sending the slave address the MCF5272 goes into receive mode and waits for a data transfer from the slave device Once a byte has been received it is stored in a read buffer previously defined in the main function The function generates its own start signal as does the i2c_write function This is case in order to allow for repeated starts In order to completely terminate a transfer the i2c_stop function must be called after the read Function prototype status i2c read uint8 slave_address uint8 buffer int byte count int freq 3 MCF5272 Soft I C User s Guide MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc 1 3 1 Arguments This section identifies the arguments for the i2c_read function It includes summaries of the input arguments and the read status byte 1 3 1 1 Input Arguments The following is a list of the 4 inputs to this function slave_address Indicates from which device the MCF5272 microprocessor reads data buffer Points to the location of the read buffer where bytes will be stored byte_count Tells the Soft IC function how many bytes will be read from the slave device freq Sets the transmission frequency 1 3 1 1 1 slave_address The slave address is a byte input that determines with which device the Soft C communicates There is no need to set or clear the LSB in order to set R W since
9. eived 1 4 IC Write Function i2c write This function performs a standard C write procedure After generating a start signal and sending the slave address it begins sending data clocked at the user defined transmission 5 MCF5272 Soft IC User s Guide MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc frequency As with the i2c_ read function the i2c_ stop function should be called to completely terminate the transmission Function prototype status i2c write uint8 slave_address uint8 buffer int byte count int freq 1 4 1 Arguments This section identifies the parameters for the i2c_write function It inclues summaries of the input parameters and the write status byte 1 4 1 1 Input Arguments The 4 inputs to this function are e slave_address Indicates to which device the MCF5272 microprocessor will be writing e buffer Pointer to the location of the write buffer from where bytes will be read e byte_count Tells the Soft C how many bytes will be written to the slave device e freq Sets the transmission frequency 1 4 1 1 1 slave_address The slave address is a byte input that determines with which device the Soft C communicates There is no need to set or clear the LSB in order to set R W since this is handled within software 1 4 1 1 2 buffer This argument points to the memory location of the write buffer Before calling any of the IC func
10. hanging Macros Logical Value to enter Macro Register gea value See in macro Binary Performed Hex PACNT init PACNT eana green AND OxFCFFFFFC PADAT init PADAT XXXO_XXXX_XXXX_XXXO AND OxEFFE PADDR init PADDR XXXO_XXXX_XXXX_XXXO AND OxEFFE SDA_high PADDR XXXO_XXXX_XXXX_XXXX AND OxEFFF SDA low PADDR XXX1_XXXX_XXXX_XXXX OR 0x1000 SCL high PADDR XXXX_XXXX_XXXX_XXX0 AND OxFFFE SCL low PADDR XXXX_XXXX_XXXX_XXX1 OR 0x0001 In order to use a different GPIO port for example Port B instead of Port A the MCF5272_ GPIO _PXXXX macros located in mcf5272 h should be switched 1 7 Hardware Interface This section discusses reasons for using the GPIO and details some issues that had to be addressed in order to make these functions work in software MOTOROLA MCF5272 Soft I C User s Guide 8 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc 1 7 1 Why GPIO The GPIO were used because they are relatively easy for a user to program PA9 and PA10 were used as the default because they are easily accessible on the M5272C3 evaluation board As mentioned in Section 1 6 2 it is extremely easy to change which GPIO pins are used 1 7 2 Using GPIO on Open Collector Lines Using the GPIO pins on open collector lines requires that a O be written to the pin s corresponding data bit in the port data register Once this is done switching the pin between input an
11. l to i2c_stop terminates communication This process can be repeated as many times as is necessary 7 MCF5272 Soft IC User s Guide MOTOROLA For More Information On This Product Go to www freescale com Freescale Semiconductor Inc 1 6 2 Changing Parameters Since it may be inconvenient for some users to use the GPIO pins that are set up by default it is possible and extremely simple to change which pins are used As mentioned in Section 1 2 PA9 and PA10 were selected for SDA and SCL in this example code In order to modify which GPIO pins are used the user should change the values in the following seven macros shown in their default setup that appear in the i2c h file define PACNT init MCF5272_GPIO PACNT amp 0xFFC3FFFF define PADDR init MCF5272 GPIO PADDR amp OxF9FF define PADAT init MCF5272_ GPIO PADAT amp OxF9FF define SDA high MCF5272_ GPIO PADDR amp OxFBFF define SDA low MCF5272 GPIO PADDR 0x0400 define SCL high MCF5272 GPIO PADDR amp OxFDFF define SCL low MCF5272 GPIO PADDR 0x0200 Each of the above macros reads one of the Port A registers and performs a logical AND OR with its contents The result sets or clears the appropriate bits in the register leaving the other bits unchanged In the following example the macros are set to use PA12 and PAO as SDA and SCL respectively Table 4 shows values that should be used in the macros to get the desired result Table 4 Example Values for C
12. ore Information On This Product Go to www freescale com Freescale Semiconductor Inc Table 1 shows acronyms along with their meanings used in this document Table 1 Acronyms and Abbreviated Terms Acronym Meaning General Purpose Input Output C Data Line C Clock Line Table 2 is a list of the documents and tools referenced in this document Table 2 References Title Order Number MCF5272 User s Manual MCF5272UM D FC Bus Specification v2 1 January 2000 http www semiconductors philips com iPort AI MIIC 201V RS 232 to PC Host Manufactured by Micro Computer Control Adapter with ASCII Interface http www mcc us com Section l Interface Description This section outlines the details of the MCF5272 Soft IC functions including the functionality of standard IC read and write features and formats Each will be analyzed at the parameter level including a description of the inputs and other parameters Section I concludes with information about the hardware interface 1 1 Software Functionality This section highlights the read and write features and delivery format of the Soft C functions Metrowerks CodeWarrior IDE v3 2 was used to develop all software described in this and subsequent sections of this manual 1 1 1 Standard Implemented The Soft IC functions as supplied by Motorola implement the standard C version 2 1 read and write procedures The following is a list of read and w
13. ransmission is successful the function will return OxAO It will NOT return OxA1 because the RXAK bit will not be set This is because the slave device always pulls SDA low on the last clock cycle After the i2c_stop function is called the status byte will be returned to its reset value of 0x81 1 5 I C Stop Function i2c_stop This generates an I C stop signal There are no inputs to this function however it does return a status byte As mentioned in both the Read and Write sections this function MUST be called after the last read write is performed in order to properly terminate the transmission Function prototype status i2c_ stop void 1 5 1 Stop Status Byte The stop status byte is identical to the status byte in the read and write functions After i2c_stop has been executed it sets the status byte to 0x81 For a complete description of the individual status byte bits see Table 3 in Section 1 3 1 1 5 1 6 Calling Sequences The following section describes how the functions should be called There are only two steps to the process GPIO initialization and reads writes 1 6 1 Read Write Calls After GPIO initialization the C communication process is very straightforward Calling either the i2c_read or i2c_write functions starts the communication process since the start signal is built into the functions Also consecutive reads and writes can be performed without calling for a stop When the transmission is finished a cal
14. rite features User definable slave address User definable read write buffer User definable byte count Programmable transmission frequency Status byte modeled after current Motorola processors with on chip C modules MOTOROLA MCF5272 Soft IC User s Guide 2 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc 1 1 2 Delivery Format The source code is provided via the ColdFire MCF5272 product page located at http motorola com coldfire 1 2 IC Init Function i2c init The Soft IC implementation uses PA9 and PA10 two Port A GPIO pins These pins were selected because they can be accessed easily through the expansion connector on the M5272C3 evaluation board The user has the flexibility to use any of the GPIO pins for establishing C communications Section 1 6 2 discusses the procedure for changing which GPIO pins are used for PC communication To initialize the GPIO pins for an IC transmission the user should call the i2c_init function This function initializes the GPIO in the PACNT register to select PA9 and PA10 and sets the appropriate values in the PADAT and PADDR registers Function code define PACNT init MCF5272 GPIO PACNT amp OxXFFC3FFFF define PADDR init MCF5272 GPIO PADDR amp OXF9OFF define PADAT init MCF5272 GPIO PADAT amp OXF9OFF void i2c_init void PACNT init PADDR init PADAT init SCL_high SDA_high 1 3 I C Read Function i2c_ r
15. tination Address Master Tx Message Bytes Enter ASCII Text or Hex 00 FF Data 6A Master Tx from iPort 6C 6E A b Default WIN J doStop Master Tx 70 irc W Master TxRx iPort Auto Repeat Received Messages V Hex Display E3 56 C2 FE00 FF 53 B1 7C 42 F9 EE 01 02 03 04 05 06 07 08 09 0A0B 0C E3 56 C2 FE00 FF 53 B1 7C 42 F9 EE Bytes to Master Rx Iv doStop Master Rx V doNack Slave Tx Message Bytes Enter ASCII Text or Hex 00 FF Data 01 02 03 04 05 06 07 08 090A 0B 0C Figure 2 iPort Data MOTOROLA MCF5272 Soft I2C User s Guide 10 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc Alternative Implementation 2 2 Alternative Interrupt Driven Implementation An alternative implementation that uses the MCF5272 s timer modules can be used for a more precise transmission frequency The example below outlines a timer implementation of the i2c_write function The main idea of this method is to have the timer module count down for half of the transmission frequency clock cycle and toggle the SCL line in the timer s interrupt service routine ISR 2 2 1 Pseudo Code Following is an example of ISR based function code for the i2c_write function Global variables isr_parity determines which value the ISR will put on SCL isr_count counts the number of times the ISR has been called isr_done indicates that th
16. tions the user must define a write buffer The size of the buffer is dependent on the specific application that the user is implementing and therefore has no maximum size requirement 1 4 1 1 3 byte_count This parameter tells the i2c_ write function how many bytes it will send to the slave device Again there is no maximum value but this parameter cannot be larger than the size of the write buffer In the case where it is random data will be transferred after the write buffer has been completely cycled through 1 4 1 1 4 freq This argument determines the transmission frequency for the read process Note that this value is passed as an integer value and is to be entered in increments of 1 Unfortunately since this calculation is based on a mathematical equation the frequency will have some margin of error MOTOROLA MCF5272 Soft I C User s Guide 6 For More Information On This Product Go to www freescale com Freescale Semiconductor Inc However for example when running from SDRAM with cache disabled on the M5272C3 reference board the entered value is close to its corresponding frequency in kHz that is 75 is about 75 kHz 1 4 1 1 5 Write Status Byte The i2c_write function also returns a status byte after execution to indicate the status of the transmission Please see Table 3 in Section 1 3 1 1 5 for a complete description of the individual bits As shown in Figure 1 the reset value of the status byte is 0x81 If a t
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18. turns a status byte after execution to indicate the status of the transmission This status byte s structure is similar to the IC Status Register ISR in other Motorola ColdFire processors such as the MCF5307 and MCF5206e The status bits included are IBB PC bus busy bit ICF data transferring bit and RXAK receive acknowledge bit The status byte configuration is outlined in Figure 1 7 6 5 4 3 2 1 0 Field ICF IBB m RXAK Reset 1000_0001 R W Read only Figure 1 Status Byte setup If a read operation is performed successfully i2c_read will return OxA1 since the bus will remain active until it is released by the i2c_stop function Table 3 Status Byte Bit Descriptions Bit Name Description ICF While one byte of data is being transferred the Data Transferring Bit is cleared Itis set by the falling edge of the 9 clock of a byte transfer 1 Transfer complete 0 Transfer in progress IBB The Bus Busy Bit indicates the status of the bus When a START signal is detected the IBB is set If a STOP signal is detected it is cleared 1 Bus is busy 0 Bus is idle RXAK The RXAK shows the value of SDA during the acknowledge bit of a bus cycle If it is low it indicates an acknowledge signal has been received after the completion of 8 bits data transmission on the bus If RXAK is high it means no acknowledge signal has been detected at the 9 clock 1 No acknowledge received 0 Acknowledge rec
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