LM3S316 Luminary Micro, Inc., LM3S316 Datasheet - Page 322

• Manufacturer Part Number: LM3S316
• Description: Microcontroller
• Manufacturer: Luminary Micro, Inc.

Inter-Integrated Circuit (I2C) Interface
14.3
322
For example:
CLK_PRD = 50 ns
TIMER_PRD = 2
SCL_LP=6
SCL_HP=4
yields a SCL frequency of:
1/T = 333 Khz
Table 14-1 gives examples of Timer period, system clock, and speed mode (Standard or Fast).
Table 14-1. Examples of I
Initialization and Configuration
The following example shows how to configure the I
This assumes the system clock is 20 MHz.
1.
2.
3.
4.
5.
6.
12.5 Mhz
16.7 Mhz
System
20 Mhz
25 Mhz
Clock
4 Mhz
6 Mhz
Enable the I
Control module.
In the GPIO module, enable the appropriate pins for their alternate function using the
GPIOAFSEL register. Also, be sure to enable the same pins for Open Drain operation.
Initialize the I
Set the desired SCL clock speed of 100 Kbps by writing the I2CMTPR register with the correct
value. The value written to the I2CMTPR register represents the number of system clock
periods in one SCL clock period. The TPR value is determined by the following equation:
TPR = (System Clock / (2 * (SCL_LP + SCL_HP) * SCL_CLK)) - 1;
TPR = (20MHz / (2 * (6 + 4) * 100000)) - 1;
TPR = 9
Write the I2CMTPR register with the value of 0x00000009.
Specify the slave address of the master and that the next operation will be a Send by writing
the I2CMSA register with a value of 0x00000076. This sets the slave address to 0x3B.
Place data (byte) to be sent in the data register by writing the I2CMDR register with the
desired data.
Period
2
Timer
0x0C
0x01
0x02
0x06
0x08
0x09
C clock by writing a value of 0x00001000 to the RCGC1 register in the System
2
C Master by writing the I2CMCR register with a value of 0x00000020.
2
96.2 Kbps
Standard
100 Kbps
100 Kbps
100 Kbps
89 Kbps
93 Kbps
C Master Timer Period versus Speed Mode
Mode
Preliminary
Period
Timer
0x01
0x02
0x02
0x03
-
-
2
C module to send a single byte as a master.
312 Kbps
278 Kbps
333 Kbps
312 Kbps
Mode
Fast
-
-
April 27, 2007