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CHAPTER 13 UART
13.6 Operations of UART Functions
UART supports four types of operating mode. Mode 0, mode 1, and mode 3 are general
serial transfer mode in which any data length can be selected in the range of 6 bits with
parity used, to 9 bits without parity used. (See Table 13.1-1 .)
■ Transferred Data Format
UART can handle data in the NRZ (Non Return to Zero) format only. Data to be transferred always begins
with the start bit ("L" level), specified number of data bits are transferred with LSB first, then data transfer
is ended with the stop bit ("H" level). Figure 13.6-1 shows the relationship between the transmit/receive
clock and transferred/received data when operating mode 0 without parity used, two stop bits, synchronous
transfer mode, and transferred data 01001101
B
(8 bits) are specified. Note that Figure 13.6-1 does not apply
to the relationship between the serial clock and serial I/O signal in asynchronous transfer mode.
Figure 13.6-1 Transferred Data Format
0
START
1
LSB
0
MSB
1
STOP
1
STOP
11 1000
Transmit/receive clock
Data to be transmitted/
received