TM4C1232E6PM Datasheet, PDF (934/1171 Pages) Texas Instruments – Tiva Microcontroller

Inter-Integrated Circuit (I²C) Interface
15.3.2.2
High-Speed Mode
The TM4C1232E6PM I²C peripheral has support for High-speed operation as both a master and
slave. High-Speed mode is configured by setting the HS bit in the I²C Master Control/Status
(I2CMCS) register. High-Speed mode transmits data at a high bit rate with a 66.6%/33.3% duty
cycle, but communication and arbitration are done at Standard, Fast mode, or Fast-mode plus
speed, depending on which is selected by the user. When the HS bit in the I2CMCS register is set,
current mode pull-ups are enabled.
The clock period can be selected using the equation below, but in this case, SCL_LP=2 and
SCL_HP=1.
SCL_PERIOD = 2 × (1 + TIMER_PRD) × (SCL_LP + SCL_HP) × CLK_PRD
So for example:
CLK_PRD = 25 ns
TIMER_PRD = 1
SCL_LP=2
SCL_HP=1
yields a SCL frequency of:
1/T = 3.33 Mhz
Table 15-3 on page 934 gives examples of timer period and system clock in High-Speed mode. Note
that the HS bit in the I2CMTPR register needs to be set for the TPR value to be used in High-Speed
mode.
Table 15-3. Examples of I²C Master Timer Period in High-Speed Mode
System Clock
40 MHz
50 MHz
80 MHz
Timer Period
0x01
0x02
0x03
Transmission Mode
3.33 Mbps
2.77 Mbps
3.33 Mbps
When operating as a master, the protocol is shown in Figure 15-7. The master is responsible for
sending a master code byte in either Standard (100 Kbps) or Fast-mode (400 Kbps) before it begins
transferring in High-speed mode. The master code byte must contain data in the form of 0000.1XXX
and is used to tell the slave devices to prepare for a High-speed transfer. The master code byte
should never be acknowledged by a slave since it is only used to indicate that the upcoming data
is going to be transferred at a higher data rate. To send the master code byte, software should place
the value of the master code byte into the I2CMSA register and write the I2CMCS register with a
value of 0x13. This places the I²C master peripheral in High-speed mode, and all subsequent
transfers (until STOP) are carried out at High-speed data rate using the normal I2CMCS command
bits, without setting the HS bit in the I2CMCS register. Again, setting the HS bit in the I2CMCS register
is only necessary during the master code byte.
When operating as a High-speed slave, there is no additional software required.
934
June 12, 2014
Texas Instruments-Production Data