Holtek HT66F30, Manual, Page: 241 / 294

Rev. 2.50 240 ��ne 22� 20�� Rev. 2.50 24� ��ne 22� 20��
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
UART Data Transfer Scheme
MSB LSB
…………………………
Transmitter Shift Register (TSR)
MSB LSB
…………………………
Receiver Shift Register (RSR)
TX Pin RX Pin
Ba�d Rate
Generator
TX Register (TXR) RX Register (RXR)
B�ffer �
B�ffer 2
B�ffer 3
Data to be transmitted Data received
UART Data Transfer Scheme
UART Commands
There are both read and write commands for the UART Module. For reading and writing to registers
both command and address information is contained within a single byte. The format for reading and
writing is shown in the following table.
Command Type Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Read FIFO 0 0 0 0 0 × × ×
Read Register 0 0 0 � 0 A2 A� A0
Write FIFO 0 0 0 0 � × × ×
Write Register 0 0 0 � � A2 A� A0
Note: "×" here stands for don't care
UART Status and Control Registers
There are six registers associated with the UART function. The USR, UCR1, UCR2 and UCR3
registers control the overall function of the UART module, while the BRG register controls the Baud
rate. The actual data to be transmitted and received on the serial interface is managed through the
TXR/RXR data register.
A[2:0] Name Reset Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
00H USR 0000 �0�� PERR NF FERR OERR RIDLE RXIF TIDLE TXIF
0�H UCR� 0000 0×00 UARTEN BNO PREN PRT STOPS TXBRK RX8 TX8
02H UCR2 0000 0000 TXEN RXEN BRGH ADDEN WAKE RIE TIIE TEIE
03H BRG ×××× ×××× BRG� BRG6 BRG5 BRG4 BRG3 BRG2 BRG� BRG0
04H UCR3 0--- ---- URST — — — — — — —
05H~0�H Un�sed ---- ---- Reserved
UART Register Summary