M37544G Mitsubishi Electric, M37544G Datasheet - Page 27

• Manufacturer Part Number: M37544G
• Description: Single-Chip 8-Bit CMOS Microcomputer
• Manufacturer: Mitsubishi Electric

[Transmit buffer register/receive buffer register (TB/RB)]
0018
The transmit buffer register and the receive buffer register are lo-
cated at the same address. The transmit buffer is write-only and
the receive buffer is read-only. If a character bit length is 7 bits, the
MSB of data stored in the receive buffer is “0”.
[Serial I/O status register (SIOSTS)] 0019
The read-only serial I/O status register consists of seven flags
(bits 0 to 6) which indicate the operating status of the serial I/O
function and various errors.
Three of the flags (bits 4 to 6) are valid only in UART mode.
The receive buffer full flag (bit 1) is cleared to “0” when the receive
buffer register is read.
If there is an error, it is detected at the same time that data is
transferred from the receive shift register to the receive buffer reg-
ister, and the receive buffer full flag is set. A write to the serial I/O
status register clears all the error flags OE, PE, FE, and SE (bit 3
to bit 6, respectively). Writing “0” to the serial I/O enable bit SIOE
(bit 7 of the serial I/O control register) also clears all the status
flags, including the error flags.
Bits 0 to 6 of the serial I/O status register are initialized to “0” at re-
set, but if the transmit enable bit of the serial I/O control register
has been set to “1”, the transmit shift completion flag (bit 2) and
the transmit buffer empty flag (bit 0) become “1”.
[Serial I/O control register (SIOCON)] 001A
The serial I/O control register consists of eight control bits for the
serial I/O function.
[UART control register (UARTCON)] 001B
The UART control register consists of four control bits (bits 0 to 3)
which are valid when asynchronous serial I/O is selected and set
the data format of an data transfer and one bit (bit 4) which is al-
ways valid and sets the output structure of the P1
[Baud rate generator (BRG)] 001C
The baud rate generator determines the baud rate for serial transfer.
The baud rate generator divides the frequency of the count source
by 1/(n + 1), where n is the value written to the baud rate generator.
16
16
16
16
16
1
/TXD pin.
• Serial I/O interrupt
When setting the transmit enable bit to “1”, the serial I/O transmit
interrupt request bit is automatically set to “1”. When not requiring
the interrupt occurrence synchronized with the transmission en-
abled, take the following sequence.
• I/O pin function when serial I/O is enabled.
The functions of P1
of a serial I/O mode selection bit and a serial I/O synchronous
clock selection bit as follows.
(1) Serial I/O mode selection bit
Clock synchronous type serial I/O is selected.
Setup of a serial I/O synchronous clock selection bit
“0” : P1
“1” : P1
Setup of a SRDY output enable bit (SRDY)
“0” : P1
“1” : P1
(2) Serial I/O mode selection bit
Clock asynchronous (UART) type serial I/O is selected.
Setup of a serial I/O synchronous clock selection bit
“0”: P1
“1”: P1
When clock asynchronous (UART) type serial I/O is selected, it is
P1
Notes on serial I/O
more instructions have been executed.
3
Set the serial I/O transmit interrupt enable bit to “0” (disabled).
Set the transmit enable bit to “1”.
Set the serial I/O transmit interrupt request bit to “0” after 1 or
Set the serial I/O transmit interrupt enable bit to “1” (enabled).
pin. It can be used as a normal I/O pin.
2
2
2
2
3
3
pin can be used as a normal I/O pin.
pin turns into an input pin of an external clock.
pin turns into an output pin of a synchronous clock.
pin turns into an input pin of a synchronous clock.
pin can be used as a normal I/O pin.
pin turns into a SRDY output pin.
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
2
and P1
MITSUBISHI MICROCOMPUTERS
3
are switched with the setting values
“1” :
“0” :
7544 Group
27