18 UNIVERSAL SERIAL INTERFACE (USI)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
18-25
A transmit buffer empty interrupt can be generated when data written to this register has been transferred
to the shift register. The subsequent transmit data can then be written, even while data is being sent.
USI Receive Data Buffer Register (USI_RD)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
USI Receive
Data Buffer
Register
(USI_RD)
0x300402
(8 bits)
D7–0 RD[7:0]
USI receive data buffer
RD7 = MSB
RD0 = LSB
0x0 to 0xff
0x0
R
D[7:0]
RD[7:0]: USI Receive Data Buffer Bits
Contains the received data. (Default: 0x0)
Serial data input from the USI_DI pin is converted to parallel, with the high level bit set to 1 and the
low level bit set to 0, and then it is loaded to this register.
A receive buffer full interrupt can be generated when the data received in the shift register has been
loaded to this register. Data can then be read until subsequent data is received.
This register is read-only.
USI UART Mode Configuration Register (USI_UCFG)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
USI
UART Mode
Configuration
Register
(USI_UCFG)
0x300440
(8 bits)
D7–4 –
reserved
–
–
–
0 when being read.
D3
UCHLN
Character length select
1 8 bits
0 7 bits
0
R/W
D2
USTPB
Stop bit select
1 2 bits
0 1 bit
0
R/W
D1
UPMD
Parity mode select
1 Even
0 Odd
0
R/W
D0
UPREN
Parity enable
1 With parity
0 No parity
0
R/W
Note: This register is effective only in UART mode. Configure USI to UART mode before setting this reg-
ister.
D[7:4]
Reserved
D3
UCHLN: Character Length Select Bit
Selects the serial transfer data length.
1 (R/W): 8 bits
0 (R/W): 7 bits (default)
When 7-bit data length is selected, D7 in the transmit data buffer is ignored and D7 in the receive data
buffer is always set to 0.
D2
USTPB: Stop Bit Select Bit
Selects the stop bit length.
1 (R/W): 2 bits
0 (R/W): 1 bit (default)
Writing 1 to USTPB selects 2 stop bits; writing 0 to it selects 1 bit. The start bit is fixed at 1 bit.
D1
UPMD: Parity Mode Select Bit
Selects the parity mode.
1 (R/W): Even parity
0 (R/W): Odd parity (default)
Parity checking and parity bit addition are enabled only when UPREN is set to 1. The UPMD setting is
disabled if UPREN is 0.
D0
UPREN: Parity Enable Bit
Enables the parity function.
1 (R/W): With parity
0 (R/W): No parity (default)
UPREN is used to select whether received data parity checking is performed and whether a parity bit
is added to transmit data. Setting UPREN to 1 parity-checks the received data. A parity bit is automati-
cally added to the transmit data. If UPREN is set to 0, no parity bit is checked or added.