HT85F2270 datasheet(215/226 Pages) HOLTEK

215 / 226 page

Rev. 1.00

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

Mode B

Mode B is an integrated full-duplex asynchronous serial communication interface. The 8 bits

of data are received via the RXD1 pin while the TXD1 pin provides the data transmit for this

communication. The data will then be transferred to the Transmit Shift Register from where it

will be shifted out onto the TXD1 pin by the UART1 Baud rate generator. The internal Baud rate

generator is enabled/disabled by the BD1 bit of the SBRCON register. The S1RELL/S1RELH

registers must be used to setup the Baud rate generator.

Data transmission is started by writing data to the S1BUF register. The TXD1 pin outputs data.

The first bit transmitted is a start bit, always “0”, then 8 bits of data, after which a stop bit, always “1”,

is transmitted.

Data to be received by the UART1 is accepted on the external RXD1 pin. When reception starts,

UART1 synchronises with the falling edge detected by the RXD1 pin. Input data is available after

one byte of data is complete in the S1BUF register and the value of the STOP bit is available as the

RB81 flag in the S1CON register. During the reception process, the S1BUF data and the RB81 bit

will remain unchanged until the process is complete.

St ar t Bi t

D 0

D 1

D 2

D 3

D 4

D 5

D 6

D 7

St op Bi t

Da ta T ra ns mi t Ti mi ng Di ag ra m

TX D1

(D at a ou t)

B aud R at e

cl oc k

St ar t Bi t

D 0

D 1

D 2

D 3

D 4

D 5

D 6

D 7

St op Bi t

Da ta R ecei ve Ti mi ng D ia gr am

RX D1

(D at a in )

Sa mp li ng R at e

UART1 Mode B Timing Diagram

HT85F2270 Datasheet(PDF) 215 Page - Holtek Semiconductor Inc

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