MC80F0424 Datasheet, PDF (87/135 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

Preliminary
MC80F0424/0432/0448
ACLK0 PIN /
ACLK1 PIN
MUX
f_XIN/2 ~ f_XIN/128
- TPS2 TPS1 TPS0 MDL3 MDL2 MDL1 MDL0
(BRGCR / BRGCR1)
5-bit counter
match
Decoder
match
5-bit counter
Internal Data Bus
RECEIVE
RXE
1/2
(Divider)
Tx_Clock
1/2
(Divider)
Rx_Clock
TXE
SEND
Figure 17-2 Baud Rate Generator Block Diagram
17.2 Serial Interface Configuration
The UART interface consists of the following hardware.
Item
Configuration
Register
Transmit shift register (TXR)
Receive buffer register (RXR)
Receive shift register
Control
register
Serial interface mode register (ASIMR)
Serial interface status register (ASISR)
Baudrate generator control register (BRGCR)
Table 17-1 Serial Interface Configuration
same address is assigned to TXR and the receive buffer
register (RXR). A read operation reads values from RXR.
Receive buffer register (RXR)
This register is used to hold receive data. When one byte of data
is received, one byte of new receive data is transferred from the
receive shift register (RXSR). When the data length is set as 7
bits, receive data is sent to bits 0 to 6 of RXR. In this case, the
MSB of RXR always becomes 0.
RXR can be read by an 8 bit memory manipulation instruction. It
cannot be written. The RESET input sets RXR to 00H.
Transmit shift register (TXR)
This is the register for setting transmit data. Data written to TXR
is transmitted as serial data. When the data length is set as 7 bit,
bit 0 to 6 of the data written to TX are transferred as transmit data.
Writing data to TXR starts the transmit operation.
TXR can be written by an 8 bit memory manipulation instruction.
It cannot be read. The RESET input sets TXR to 0FFH.
Note: Do not write to TXR during a transmit operation. The
Note: The same address is assigned to RXR and the
transmit shift register (TXR). During a write operation, val-
ues are written to TXR.
Receive shift register
This register converts serial data input via the RxD pin to paral-
leled data. When one byte of data is received at this register can-
not be manipulated directly by a program.
MAR. 2005 Ver 0.2
83