20 GENERAL-PURPOSE SERIAL INTERFACE (FSIO)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
20-23
FSIO Ch.
x
Transmit Data Registers (FSIO_TXD
x
)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
FSIO Ch.
x
Transmit Data
Register
(FSIO_TXD
x
)
0x300700
0x300710
(8 bits)
D7–0 TXD[7:0]
Transmit data
TXD7(6) = MSB
TXD0 = LSB
0x0 to 0xff (0x7f)
X
R/W 7-bit asynchronous
mode does not use
TXD7.
D[7:0]
TXD
x
[7:0]: Transmit Data Bits
Sets transmit data. (Default: indeterminate)
When data is written to this register (transmit data buffer) after 1 is written to TXEN/FSIO_CTL
x
regis-
ter, a transmit operation begins. The data written to TXD[7:0] enters the transmit data buffer and waits
for transmission. The transmit data buffer is a 2-byte FIFO and up to two data can be written to it suc-
cessively if empty. Older data will be transmitted first and cleared after transmission. When all the data
in the transmit data buffer are transferred, a cause of transmit-data empty interrupt occurs.
In 7-bit asynchronous mode, TXD7 (MSB) is ignored.
The serial-converted data is output from the SOUT
x
pin beginning with the LSB, in which the bits set
to 1 are output as high-level signals and those set to 0 output as low-level signals.
This register can be read as well as written.
FSIO Ch.
x
Receive Data Registers (FSIO_RXD
x
)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
FSIO Ch.
x
Receive Data
Register
(FSIO_RXD
x
)
0x300701
0x300711
(8 bits)
D7–0 RXD[7:0]
Receive data
RXD7(6) = MSB
RXD0 = LSB
0x0 to 0xff (0x7f)
X
R 7-bit asynchronous
mode does not use
RXD7 (fixed at 0).
D[7:0]
RXD
x
[7:0]: Receive Data Bits
The data in the receive data buffer can be read from this register beginning with the oldest data first.
The received data enters the receive data buffer. The receive data buffer is a 4-byte FIFO and can re-
ceive data until it becomes full unless received data is not read out. When the buffer is full and also the
shift register contains received data, an overrun error will occur if the received data is not read until the
next data receiving begins. The receive buffer status flag RDBF/FSIO_STATUS
x
register is provided
to indicate that it is necessary to read the receive data buffer. This flag is set to 1 when the receive data
buffer contains one or more received data, and is reset to 0 when the receive data buffer becomes empty
by reading all the received data.
When the receive data buffer has received the number of data specified with FIFOINT[1:0]/FSIO_
IRDA
x
register (one data in standard mode), a cause of receive buffer full interrupt occurs.
In 7-bit asynchronous mode, 0 is stored in RXD7.
The serial data input from the SIN
x
pin is converted into parallel data beginning with the LSB, with the
high-level signals changed to 1s and the low-level signals changed to 0s. The resulting data is stored in
this buffer.
This register is a read-only register, so no data can be written to it. (Default: indeterminate)
FSIO Ch.
x
Status Registers (FSIO_STATUS
x
)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
FSIO Ch.
x
Status Register
(FSIO_
STATUS
x
)
0x300702
0x300712
(8 bits)
D7–6 RXDNUM
[1:0]
Receive FIFO data count
RXDNUM[1:0] Number of data 0x0
R
0x3
0x2
0x1
0x0
4
3
2
1 or 0
D5
TEND
Transmit status flag
1 Busy
0 End/Idle
0
R
D4
FER
Framing error flag
1 Error
0 Normal
0
R/W Reset by writing 0.
D3
PER
Parity error flag
1 Error
0 Normal
0
R/W
D2
OER
Overrun error flag
1 Error
0 Normal
0
R/W
D1
TDBE
Transmit data buffer empty flag
1 Empty
0 Full
1
R
D0
RDBF
Receive data buffer status flag
1 Contained
0 Not contained
0
R
D[7:6]
RXDNUM[1:0]: Receive FIFO Data Count Bits
Indicates the number of data in the receive data buffer (FIFO) that have not been read.