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Usart operation – FUJITSU MB91460 SERIES FR60 User Manual

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Chapter 32 USART (LIN / FIFO)

7.USART Operation

7. USART Operation

USART operates in operation mode 0 for normal bidirectional serial communication, in mode 2
and 3 in bidirectional communication as master or slave, and in mode 1 as master or slave in
multiprocessor communication.

Operation of USART

• Operation modes

There are four USART operation modes: modes 0 to 3. As listed in table

7-1

, an operation mode can be

selected according to the inter-CPU connection method and data transfer mode.

* means the data bit transfer format: LSB or MSB first

** "+1" means the indicator bit of the address/data selection in the multiprocessor mode, instead of parity.

(Note)

Mode 1 operation is supported both for master or slave operation of USART in a master-slave
connection system. In Mode 3 the USART function is locked to 8N1-Format, LSB first.

If the mode is changed, USART cuts off all possible transmission or reception and awaits then new action.

Inter-CPU Connection Method

External Clock One-to-one connection (normal mode) and master-slave connection (multiprocessor mode) can
be selected. For either connection method, the data length, whether to enable parity, and the synchronization
method must be common to all CPUs. Select an operation mode as follows:

• In the one-to-one connection method, operation mode 0 or 2 must be used in the two CPUs. Select

operation mode 0 for asynchronous transfer mode and operation mode 2 for synchronous transfer mode.

Note, that one CPU has to set to the master and one to the slave in synchronous mode 2.

• Select operation mode 1 for the master-slave connection method and use it either for the master or slave

system.

Synchronization Methods

In asynchronous operation USART reception clock is automatically synchronized to the falling edge of a
received start bit.

In synchronous mode the synchronization is performed either by the clock signal of the master device or by
USART itself if operating as master.

Signal Mode

USART can treat data in non-return to zero (NRZ) and return to zero (RZ) format. For this option the ECCR:
INV bit is provided.

Operation Enable Bit

USART controls both transmission and reception using the operation enable bit for transmission (SCR04:

Table 7-1 USART operation mode

Operation

mode

Data length

Synchroniza-

tion of mode

Length

of

stop bit

data bit

directio

n*

parity

disabled

parity

enabled

0

normal mode

7 or 8

asynchronous

1 or 2

L/M

1

multiprocessor

7 or 8 + 1**

-

asynchronous

1 or 2

L/M

2

normal mode

8

synchronous

0, 1 or 2

L/M

3

LIN mode

8

-

asynchronous

1

L