
390
CHAPTER 13 UART
MB90560 series
13.7
13.7.2 Operation in Synchronous Mode (Operation Mode 2)
Operation of UART
The clock synchronous transfer method is used for UART operation mode 2 (normal
mode).
I
Operation in Synchronous Mode (Operation Mode 2)
G
Transfer data format
In synchronous mode, 8-bit data is transferred using the LSB first method, in which start and
stop bits are not added. Figure 13.7-3 shows the data format in clock synchronous mode.
Figure 13.7-3 Transfer data format (operation mode 2)
G
Clock Supply
In clock synchronous mode (I/O extended serial), as same number of clock as the number of
transmission and reception bits must be supplied.
When the internal clock (dedicated baud rate generator or internal timer) is selected, the data
receiving synchronous clocks is generated automatically if data is transmitted.
When the external clock is selected, confirm that the transmission side UART serial output
data register (SODR0/1) contains data (SSR0/1: TDRE=0). Then, clocks for just “1” byte must
be supplied from outside.
The mark level (“H”) must be retained before transmission starts and after it is complete.
G
Error Detection
Only overrun errors can be detected; parity and framing errors cannot be detected.
1
0
1
1
0
RXE, TXE
LSB
MSB
Transmission data writing
Transmitting and receiving
clocks
Transmission and receive
data
Data
Mark level
0
1
0