MC908AP8CFBE Datasheet, PDF (248/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Multi-Master IIC Interface (MMIIC)
14.9 SMBus Protocol Implementation
Shaded data packets indicate transmissions by the MCU
MASTER MODE
START Address 0 ACK Command ACK START Address 1 ACK RX Data1 ACK
ACK RX DataN NAK STOP
OPERATION:
Prepare for repeated START
FLAGS:
MMTXIF set
MMRXAK clear
ACTION:
1. Set MMRW
2. Set REPSEN
3. Clear MMTXAK
4. Load dummy ($FF) to MMDTR
OPERATION:
Prepare for Master mode
ACTION:
1. Load slave address to MMADR
2. Clear MMRW
3. Load command to MMDTR
4. Set MMAST
OPERATION:
Get ready to receive data
FLAGS:
MMTXIF set
MMRXAK clear
ACTION:
Load dummy ($FF) to MMDTR
OPERATION:
Read received data
FLAGS:
MMRXIF set
ACTION:
Read Data1 from MMDRR
OPERATION:
Generate STOP
FLAGS:
MMRXIF set
ACTION:
Read DataN from MMDRR
OPERATION:
Read received data and prepare for STOP
FLAGS:
MMRXIF set
ACTION:
1. Set MMTXAK
2. Read Data(N-1) from MMDRR
3. Clear MMAST
SLAVE MODE
START Address 0 ACK Command ACK START Address 1 ACK TX Data1 ACK
ACK TX DataN NAK STOP
OPERATION:
Slave address match and
check for data direction
FLAGS:
MMRXIF set
MMATCH set
MMSRW depends on 8th
bit of calling address byte
ACTION:
1. Check MMSRW
2. Read Slave address
OPERATION:
Slave address match and
get ready to transmit data
FLAGS:
MMRXIF set
MMATCH set
MMSRW depends on 8th
bit of calling address byte
ACTION:
Check MMSRW
OPERATION:
Transmit data
FLAGS:
MMTXIF set
MMRXAK clear
ACTION:
Load Data3 to MMDTR
OPERATION:
Last data sent
FLAGS:
MMTXIF set
MMRXAK set
ACTION:
Load dummy ($FF) to MMDTR
OPERATION:
Prepare for Slave mode
ACTION:
1. Load slave address to MMADR
2. Clear MMTXAK
3. Clear MMAST
OPERATION:
Read and decode received command
FLAGS:
MMRXIF set
MMATCH clear
ACTION:
Load Data1 to MMDTR
OPERATION:
Transmit data
FLAGS:
MMTXIF set
ACTION:
Load Data2 to MMDTR
OPERATION:
Last data is going to be sent
FLAGS:
MMTXIF set
MMRXAK clear
ACTION:
Load dummy ($FF) to MMDTR
Figure 14-20. SMBus Protocol Implementation
MC68HC908AP Family Data Sheet, Rev. 4
246
Freescale Semiconductor