
I
2
C Interface
Freescale Semiconductor
32-7
32.3
Functional Description
The I
2
C module uses a serial data line (I2C_SDA) and a serial clock line (I2C_SCL) for data transfer. For
I
2
C compliance, all devices connected to these two signals must have open drain or open collector outputs.
The logic AND function is exercised on both lines with external pull-up resistors.
Out of reset, the I
2
C default state is as a slave receiver. Therefore, when not programmed to be a master or
responding to a slave transmit address, the I
2
C module should return to the default slave receiver state. See
Section 32.4.1, “Initialization Sequence,”
for exceptions.
Normally, a standard communication is composed of four parts: START signal, slave address transmission,
data transfer, and STOP signal. These are discussed in the following sections.
32.3.1
START Signal
When no other device is bus master (I2C_SCL and I2C_SDA lines are at logic high), a device can initiate
communication by sending a START signal (see A in
). A START signal is defined as a
high-to-low transition of I2C_SDA while I2C_SCL is high. This signal denotes the beginning of a data
transfer (each data transfer can be several bytes long) and awakens all slaves.
Address: 0xFC05_8010 (I2DR)
Access: User read/write
7
6
5
4
3
2
1
0
R
DATA
W
Reset:
0
0
0
0
0
0
0
0
Figure 32-6. I
2
C Data I/O Register (I2DR)
Table 32-6. I2DR Field Description
Field
Description
7–0
DATA
I
2
C data. When data is written to this register in master transmit mode, a data transfer is initiated. The most significant
bit is sent first. In master receive mode, reading this register initiates the reception of the next byte of data. In slave
mode, the same functions are available after an address match has occurred.
Note: In master transmit mode, the first byte of data written to I2DR following assertion of I2CR[MSTA] is used for
the address transfer and should comprise the calling address (in position D7–D1) concatenated with the
required R/W bit (in position D0). This bit (D0) is not automatically appended by the hardware, software must
provide the appropriate R/W bit.
Note: I2CR[MSTA] generates a start when a master does not already own the bus. I2CR[RSTA] generates a start
(restart) without the master first issuing a stop (i.e., the master already owns the bus). To start the read of data,
a dummy read to this register starts the read process from the slave. The next read of the I2DR register
contains the actual data.
MCF5329 Reference Manual, Rev 3
Содержание MCF5329
Страница 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 126: ...Enhanced Multiply Accumulate Unit EMAC 4 20 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 564: ...Liquid Crystal Display Controller LCDC 22 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 692: ...Programmable Interrupt Timers PIT0 PIT3 28 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 720: ...Queued Serial Peripheral Interface QSPI 30 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 790: ...Message Digest Hardware Accelerator MDHA 33 20 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 902: ...Register Memory Map Quick Reference A 26 Freescale Semiconductor MCF5329 Reference Manual Rev 3...