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CHAPTER 15 UART
15.9 UART Operations
The UART has an ordinary bidirectional serial communication function (operation
modes 0 and 2) and master/slave-type connection communication function (operation
mode 1).
I UART operations
❍ Operation mode
The UART has three operation modes, mode 0 to mode 2. The inter-CPU connection method
and data transfer method can be used to select the operation mode as shown in Table 15.9-1
"UART operation modes".
Table 15.9-1 UART operation modes
Operation mode
0
Normal mode
1
Multiprocessor mode
2
Normal mode
-:
Setting is disabled.
*1:
+1 is the address/data selection bit (A/D) used for communication control.
*2:
Only one bit can be detected as stop bit at reception.
Note:
UART operation mode 1 is only used for the master unit in master/slave-type connection.
❍ Inter-CPU connection method
One-to-one connection (normal mode) or master/slave-type connection (multiprocessor mode)
can be selected. With either method, the data length, whether to use parity, and the
synchronization method must be the same for all CPUs. The operation mode is selected as
shown below.
•
In a one-to-one connection, the two CPUs must use the same operation mode (operation
mode 0 or 2). For the asynchronous method, select operation mode 0. For the synchronous
method, select operation mode 2.
•
In the master/slave-type connection, use operation mode 1. Select operation mode 1 and
use the unit as the master. In this connection, select no parity.
❍ Synchronization method
For the operation mode, the asynchronous method (start-stop synchronization) or clock
synchronization method can be selected.
334
Data length
Without parity
With parity
7 bits or 8 bits
8 + 1 (*1)
8
Synchronization
method
Asynchronous
-
Asynchronous
-
Synchronous
Stop-bit length
1 bit or 2 bits (*2)
None
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