7643 datasheet(176/424 Pages) RENESAS

176 / 424 page

Rev.2.00

Aug 28, 2006

page 55 of 202

7643 Group

REJ09B0133-0200

APPLICATION

2.4 UART

(2) UART address mode

qOperation explanation

The UART address mode is intended for use to communicate between the specified MCUs in

a multi-MCU environment. The UART address mode can be used in either an 8-bit or 9-bit

character length. An address is identified by the MSB of the incoming data being “1”. The bit

is “0” for non-address data.

When the MSB of the incoming data is “0” in the UART address mode, the Receive Buffer Full

Flag is set to “1”, but the Receive Buffer Full Interrupt Request Bit is not set to “1”. When the

MSB of the incoming data is “1”, normal receive operation is performed. In the UART address

mode an overrun error is not detected for reception of the 2nd and onward bytes. An occurrence

of framing error or parity error sets the Summing Error Interrupt Request Bit to “1” and the data

is not received independent of its MSB contents.

Usage of UART address mode is explained as follows:

(1) Set the UART Address Mode Enable Bit to “1”.

(2) Sends the address data of a slave MCU first from a host MCU to all slave MCUs. The MSB

of address data must be “1” and the remaining 7 bits specify the address.

(3) The all slave MCUs automatically check for the received data whether its stop bit is valid

or not, and whether the parity error occurs or not (when the parity enabled). If these errors

occur, the Framing Error Flag or Parity Error Flag and the Summing Error Flag are set to

“1”. Then, the Summing Error Interrupt Request Bit is also set to “1”.

(4) When received data has no error, the all slave MCUs must judge whether the address of

the received address data matches with their own addresses by a program. After the MSB

being “1” is received, the UART Address Mode Enable Bit is automatically set to “0” (disabled).

(5) The UART Address Mode Enable Bit of the slave MCUs which have be judged that the

address does not match with them must be set to “1” (enabled) again by a program to

disable reception of the following data.

(6) Transmit the data of which MSB is “0” from the host MCU. The slave MCUs disabling the

UART address mode receive the data, and their Receive Buffer Full Flags and the Receive

Buffer Full Interrupt Request Bits are set to “1”. For the other slave MCUs enabling the

UART address mode, their Receive Buffer Full Flag are set to “1”, but their Receive Buffer

Full Interrupt Request Bits are not set to “1”.

(7) An overrun error cannot be detected after the first data has been received in UART Address

Mode. Accordingly, even if the slave MCUs does not read the received data and the next

data has been received, an overrun error does not occur.

Thus, a communication between a host MCU and the specified MCU can be realized.

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