APPLICATION
2.5 Serial I/O1
3820 GROUP USER’S MANUAL
2–122
(2) Serial I/O1 status register (SIO1STS)
This register (address 0019
16
) 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/O1 status register
I
Transmit buffer empty flag (bit 0)
This flag 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.
I
Receive 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.
b7b6 b5b4b3 b2b1b0
Serial I/O1 status register (SIO1STS) [Address 19
16
]
B
0
At reset R W
0
Serial I/O1 status register
1
2
3
4
5
6
7
0
0
0
0
0
0
1
Name
Functions
Transmit buffer
empty flag (TBE)
Receive buffer full flag
(RBF)
Transmit shift register shift
completion flag (TSC)
Overrun error flag
(OE)
Parity error flag
(PE)
Framing error flag
(FE)
Summing error flag
(SE)
0: Buffer full
1: Buffer empty
0: Buffer empty
1: Buffer full
0: Transmit shift in progress
1: Transmit shift completed
0: No error
1: Overrun error
0: No error
1: Parity error
0: No error
1: Framing error
0: (OE) U (PE) U (FE) = 0
1: (OE) U (PE) U (FE) = 1
Nothing is allocated. This bit cannot be written to
and is fixed to “1” at reading.
×
×
×
×
×
×
×
×
1