APPLICATION
2.5 Serial I/O
3822 GROUP USER’S MANUAL
2–121
(2) Serial I/O status register (address 001916)
This register consists of the following flags:
flags representing the states of the registers used for transmission/reception
error flags.
This is a read-only register.
Bit 7 is unused and set to “1” at reading.
Fig. 2.5.15 Structure of serial I/O status register
sTransmit buffer empty flag (bit 0)
This bit is automatically cleared to “0” by writing transmit data into the transmit buffer register.
After the transmit data is written in the transmit buffer register, it is transferred to the transmit shift
register. When this transfer is completed and the transmit buffer register becomes empty, this flag is
automatically is set to “1.”
It is possible to write transmit data into the transmit buffer register only while the transmit buffer empty
flag is “1.”
This flag is valid in both the clock synchronous mode and the UART mode.
sReceive buffer full flag (bit 1)
When all receive data has been input to the receive shift register and then this receive data is
transferred to the receive buffer register, this flag is automatically is set to “1.”
When the transferred receive data is read out from the receive buffer register, the flag is automatically
is cleared to “0.”
If all the next receive data is input to the receive shift register when the receive buffer flag is “1” (the
receive buffer register is not yet read out), the overrun error flag is set to “1.”
This flag is valid in both the clock synchronous mode and the UART mode.
b7 b6 b5 b4 b3 b2 b1 b0
Serial I/O status register (SIOSTS) [Address 19 16]
B
At reset R W
Serial I/O status register
0
1
2
3
4
5
6
7
0
1
Name
Functions
Transmit buffer
empty flag (TBE)
0: Buffer full
1: Buffer empty
Receive buffer full flag
(RBF)
0: Buffer empty
1: Buffer full
Transmit shift register shift
completion flag (TSC)
0: Transmit shift in progress
1: Transmit shift completed
Overrun error flag
(OE)
0: No error
1: Overrun error
Parity error flag
(PE)
0: No error
1: Parity error
Framing error flag
(FE)
0: No error
1: Framing error
Nothing is allocated. This bit cannot be written to
and is fixed to “1” at reading.
Summing error flag
(SE)
0: (OE) U (PE) U (FE) = 0
1: (OE) U (PE) U (FE) = 1
×
1