CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U12688EJ4V0UM00
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10.2.2 Configuration
UARTn is controlled by the asynchronous serial interface mode registers (ASIMn0, ASIMn1) and the asynchronous
serial interface status registers (ASISn) (n = 0, 1). Receive data is held in the receive buffer (RXBn) and transmit data
is written in the transmit shift registers (TXSn).
The asynchronous serial interface is configured as shown in Figure 10-1.
(1) Asynchronous serial interface mode registers (ASIM00, ASIM01, ASIM10, ASIM11)
The ASIMn0 and ASIMn1 registers are 8-bit registers that specify asynchronous serial interface operations.
(2) Asynchronous serial interface status registers (ASIS0, ASIS1)
The ASISn registers are registers of flags that show the contents of errors when a receive error occurs and
transmission status flags. Each receive error flag is set (1) when a receive error occurs and is cleared (0) by
reading of data from the receive buffer (RXBn) or reception of the next new data (if there is an error in the next
data, that error flag will not be cleared (0) but left set (1)).
The transmit status flag is set (1) when transmission starts and is cleared (0) when transmission ends.
(3) Receive control parity check
Receive operations are controlled according to the contents set in the ASIMn0 and ASIMn1 registers. Also,
errors such as parity errors are checked during receive operations. If an error is detected, a value
corresponding to the error content is set in the ASISn register.
(4) Receive shift register
This is a shift register that converts serial data input to the RXDn pin to parallel data. When 1 byte of data is
received, the receive data is transferred to the receive buffer.
This register cannot be directly manipulated.
(5) Receive buffers (RXB0, RXB0L, RXB1, RXB1L)
RXBn are 9-bit buffer registers that hold receive data, and when 7 or 8-bit character data is received, a 0 is
stored in the higher bits.
During 16-bit access of these registers, specify RXB0 and RXB1, and during lower 8-bit access, specify
RXB0L and RXB1L.
In the receive enabled state, 1 frame of receive data is transmitted to the receive buffer from the receive shift
register in synchronization with the termination of shift-in processing.
Also, a reception complete interrupt request (INTSRn) is generated when data is transmitted to the receive
buffer.
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