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13.3
Operation
13.3.1
Overview
The SCI can carry out serial communication in two modes: asynchronous mode in which
synchronization is achieved character by character, and synchronous mode in which
synchronization is achieved with clock pulses. A smart card interface is also supported as a serial
communication function for an IC card interface.
Selection of asynchronous or synchronous mode and the transmission format for the normal serial
communication interface is made in SMR, as shown in table 13.8. The SCI clock source is
selected by the C/A bit in SMR and the CKE1 and CKE0 bits in SCR, as shown in table 13.9.
For details of the procedures for switching between LSB-first and MSB-first mode and inverting
the data logic level, see section 14.2.1, Smart Card Mode Register (SCMR).
For selection of the smart card interface format, see section 14.3.3, Data Format.
Asynchronous Mode
• Data length is selectable: 7 or 8 bits
• Parity and multiprocessor bits are selectable, and so is the stop bit length (1 or 2 bits). These
selections determine the communication format and character length.
• In receiving, it is possible to detect framing errors, parity errors, overrun errors, and the break
state.
• An internal or external clock can be selected as the SCI clock source.
When an internal clock is selected, the SCI operates using the on-chip baud rate generator,
and can output a serial clock signal with a frequency matching the bit rate.
When an external clock is selected, the external clock input must have a frequency 16 times
the bit rate. (The on-chip baud rate generator is not used.)
Synchronous Mode
• The communication format has a fixed 8-bit data length.
• In receiving, it is possible to detect overrun errors.
• An internal or external clock can be selected as the SCI clock source.
When an internal clock is selected, the SCI operates using the on-chip baud rate generator,
and can output a serial clock signal to external devices.
When an external clock is selected, the SCI operates on the input serial clock. The on-chip
baud rate generator is not used.
Section 13 Serial Communication Interface
Rev. 4.00 Jan 26, 2006 page 507 of 938
REJ09B0276-0400
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