18 UNIVERSAL SERIAL INTERFACE (USI)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
18-1
Universal Serial Interface (USI)
18
USI Module Overview
18.1
The S1C33L26 incorporates a universal serial interface (USI) module that can be configured as a UART, SPI, or
I
2
C interface unit by the software switch.
The following shows the main features of USI:
• Supports five interface modes: UART, SPI master, SPI slave, I
2
C master, and I
2
C slave modes.
• Contains one-byte receive data buffer and one-byte transmit buffer.
• Supports both MSB first and LSB first modes.
• UART mode
- Character length: 7 or 8 bits
- Parity mode: even, odd, or no parity
- Stop bit: 1 or 2 bits
- Start bit: 1 bit fixed
- Parity error, framing error, and overrun error detectable
- Can generate receive buffer full, transmit buffer empty, and receive error interrupts.
- Supports DMA transfer.
• SPI master/slave mode
- Data length: 8 or 9 bits (master mode), or 8 bits fixed (slave mode)
- Supports both fast and normal modes (master mode), or normal mode only (slave mode).
- Data transfer timing (clock phase and polarity variations) is selectable from among 4 types.
- Can generate receive buffer full, transmit buffer empty, and receive error interrupts.
- Supports DMA transfer.
• I
2
C master/slave mode
- 7-bit addressing mode (10-bit addressing is possible by software control.)
- Supports single master configuration only (master mode).
- Supports clock stretch/wait functions.
- Can generate operation (start/stop, data transfer, ACK/NAK transfer) completion interrupts and receive error
interrupts.
Figure 18.1.1 shows the USI configuration.
Shift register
Receive data
buffer (1 byte)
USI_DI
Internal bus
ITC
USI
Bus I/F
and
control
registers
USI_CK
USI_CS
Shift register
Transmit data
buffer (1 byte)
Clock/transfer control
USI_DO
Interrupt
control
Transfer clock source
(T8 Ch.0)
1.1 USI Configuration
Figure 18.