ATA6603-EK Atmel, ATA6603-EK Datasheet - Page 210

• Manufacturer Part Number: ATA6603-EK
• Description: MCU, MPU & DSP Development Tools Demoboard LIN-MCM
• Manufacturer: Atmel

Specifications of ATA6603-EK

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.17.8.1
4.17.9
4.17.9.1
210
ATA6602/ATA6603
USART Register Description
Using MPCMn
USART I/O Data Register n– UDRn
For an MCU to act as a master MCU, it can use a 9-bit character frame format (UCSZn = 7). The
ninth bit (TXB8n) must be set when an address frame (TXB8n = 1) or cleared when a data frame
(TXB = 0) is being transmitted. The slave MCUs must in this case be set to use a 9-bit character
frame format.
The following procedure should be used to exchange data in Multi-processor Communication
mode:
Using any of the 5- to 8-bit character frame formats is possible, but impractical since the
Receiver must change between using n and n+1 character frame formats. This makes
full-duplex operation difficult since the Transmitter and Receiver uses the same character size
setting. If 5- to 8-bit character frames are used, the Transmitter must be set to use two stop bit
(USBSn = 1) since the first stop bit is used for indicating the frame type.
Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCMn bit. The
MPCMn bit shares the same I/O location as the TXCn Flag and this might accidentally be
cleared when using SBI or CBI instructions.
The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers share the
same I/O address referred to as USART Data Register or UDRn. The Transmit Data Buffer Reg-
ister (TXB) will be the destination for data written to the UDRn Register location. Reading the
UDRn Register location will return the contents of the Receive Data Buffer Register (RXB).
For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter and set to
zero by the Receiver.
1. All Slave MCUs are in Multi-processor Communication mode (MPCMn in
2. The Master MCU sends an address frame, and all slaves receive and read this frame.
3. Each Slave MCU reads the UDRn Register and determines if it has been selected. If
4. The addressed MCU will receive all data frames until a new address frame is received.
5. When the last data frame is received by the addressed MCU, the addressed MCU sets
Initial Value
Read/Write
Bit
UCSRnA is set).
In the Slave MCUs, the RXCn Flag in UCSRnA will be set as normal.
so, it clears the MPCMn bit in UCSRnA, otherwise it waits for the next address byte and
keeps the MPCMn setting.
The other Slave MCUs, which still have the MPCMn bit set, will ignore the data frames.
the MPCMn bit and waits for a new address frame from master. The process then
repeats from 2.
R/W
7
0
R/W
6
0
R/W
5
0
R/W
4
0
RXB[7:0]
TXB[7:0]
R/W
3
0
R/W
2
0
R/W
1
0
R/W
0
0
4921E–AUTO–09/09
UDRn (Write)
UDRn (Read)