UPD784020 Datasheet, PDF (38/90 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCOMPUTER

mPD784020, 784021
8.8.1 Asynchronous Serial Interface/Three-Wire Serial I/O (UART/IOE)
Two serial interface channels are available; for each channel, asynchronous serial interface mode or three-wire
serial I/O mode can be selected.
(1) Asynchronous serial interface mode
In this mode, 1-byte data is transferred after a start bit.
A baud rate generator is incorporated to enable communication at a wide range of baud rates.
Moreover, the frequency of a clock signal applied to the ASCK pin can be divided to define a baud rate.
With the baud rate generator, the baud rate conforming to the MIDI standard (31.25 kbps) can be obtained.
Fig. 8-10 Block Diagram of Asynchronous Serial Interface Mode
Internal bus
Receive buffer RXB, RXB2
RxD, RxD2
TxD, TxD2
Baud rate generator
fXX/2
ASCK, ASCK2
Receive
shift register
Transmission
shift register
TXS, TXS2
Reception
control parity
check
INTSR,
INTSR2
INTSER,
INTSER2
Transmission
control parity
bit addition
INTST, INTST2
1/2 ⁿ⁺¹
1/2m
1/2m
Remark fXX: Oscillator frequency or external clock input
n = 0 to 11
m = 16 to 30
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