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CHAPTER 15 SERIAL INTERFACE UART2
307
User
’
s Manual U14260EJ3V1UD
(c) Reception
The interface enters the reception wait status if the infrared data transfer (IrDA) mode is specified by using
transfer mode specification register 2 (TRMC2) and bit 7 (POWER2) of asynchronous serial interface mode
register 2 (ASIM2) is set to 1 and then bit 5 (RXE2) is set to 1. In this status, the R
X
D2 pin is monitored
to detect the start bit. When the start bit is detected, reception is started, and serial data is sequentially
stored in receive shift register 2 (RX2) at the specified baud rate.
When the stop bit is received, the data in RX2 is written to receive buffer register 2 (RXB2). If an overrun
error (OVE2) occurs, however, the receive data is not written to RXB2 but discarded. Even if a parity error
(PE2) or framing error (FE2) occurs during reception, reception continues up to the position at which the
stop bit is received, and an error interrupt (INTSR2/INTSER2) occurs after completion of reception.
Figure 15-25. Timing of Receive Completion Interrupt Request in Infrared Data Transfer (IrDA) Mode
D0
Start
Parity
Stop
D1
D2
D3
D4
D5
D6
D7
R
X
D2 (input)
INTSR2
RXB2
76H
Cautions 1. Be sure to read receive buffer register 2 (RXB2) even if a reception error has occurred.
Otherwise, an overrun error will occur when the next data is received, and the reception
error status will persist.
2. The number of stop bits is always 1 during reception. A second stop bit is ignored.
(d) Bit rate and pulse width
Table 15-12 shows the bit rate and pulse width in the infrared data transfer (IrDA) mode.
The rated minimum pulse width is 1.41
μ
s, and the maximum pulse width is the sum of 3/16 of the bit rate
and 2.5% of the bit cycle or 1.08
μ
s, whichever is greater.
Table 15-12. Bit Rate and Pulse Width
Bit Rate (bps)
Allowable Bit Rate Error
(% of Bit Rate)
Minimum Pulse Width
(
μ
s)
Nominal Value of
3/16 of Pulse Width
(
μ
s)
Maximum Pulse Width
(
μ
s)
2400
+/
–
0.87
1.41
78.13
88.55
9600
19.53
22.13
19200
9.77
11.07
38400
4.88
5.96
57600
3.26
4.34
115200
1.63
2.71