Uart Operation - Fujitsu FR60 Hardware Manual

13.3 UART Operation

The UART has two operating modes: asynchronous (start-stop synchronization) mode
and CLK synchronous mode.
Asynchronous (start-stop synchronization) mode consists of normal and
multiprocessor modes.
This section describes the operation of these operating modes.
■ UART Operating Modes
The UART has the operating modes shown in Table 13.3-1. Set a value in the SMR and SCR
registers to switch mode.
Table 13.3-1 UART Operating Modes
Mode Parity
Yes/No
0
Yes/No
1 No
2 No
Note:
The stop bit length in asynchronous (start-stop synchronization) mode can be specified only for a
send operation. The stop bit length is always one bit for a receive operation. Since operation is
possible only in the above modes, do not make any other setting.
■ Selecting a Clock for the UART
❍ Internal timer
If you select the U-TIMER by setting CS0 to "0", the baud rate is determined according to the
reload value set for the U-TIMER. At this time, you can calculate the baud rate as follows:
Asynchronous (start-stop synchronization): φ/(16 x β)
CLK synchronous:
φ: Peripheral machine clock frequency (CLKP)
β: Cycle specified for the U-TIMER (2n+2 or 2n+3, or n is the reload value.)
In asynchronous (start-stop synchronization) mode, data can be transferred in the range from
-1% to +1% of the specified baud rate.
❍ External clock
If you select an external clock by setting CS0 to "1", the baud rate is as follows (the frequency of
the external clock is assumed to be f):
Asynchronous (start-stop synchronization): f/16
CLK synchronous:
However, the maximum value for f is 3.125 MHz.
Data length
7
Asynchronous (start-stop synchronization)
8
Asynchronous (start-stop synchronization)
8+1
8
Operating mode
normal mode
multiprocessor mode
CLK synchronous mode
φ/β
f
CHAPTER 13 UART
Stop bit length
1 bit
or
2 bits
No
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