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Chapter 5 Serial Functions
97
■ Reception
(1) Select the synchronous serial interface by setting the SC0CMD flag of the
serial interface 0 control register (SC0CTR) to "0."
(2) Select the transfer bit count with the SC0LNG2 to 0 flags of the serial
interface 0 mode register 0 (SC0MD0). The transfer bit count can be set as
1 to 8 bits.
(3) Specify whether the start condition is enabled or disabled with the SC0STE
flag of the SC0MD0 register.
(4) Specify the first bit to be transferred (MSB first or LSB first) with the
SC0DIR flag of the SC0MD0 register.
(5) Select the valid edge of the clock signal with the SC0CE1 to 0 flags of the
SC0MD0 register.
(6) When the clock source is an internal clock:
• Select the clock source with the SC0CK1 to 0 flags of serial interface 0
mode register 1 (SC0MD1).
• Set the SC0CKM flag of the SC0MD1 register to specify whether or not
the clock source frequency will be divided by 8.
• Select serial clock pin operation by setting the SC0SBTS flag of the
serial interface 0 mode register 3 (SC0MD3) to "1."
• Set the SC0SBTM flag of the SC0MD3 register.
• Set bit 2 of the port 0 direction control register (P0DIR) to the output
mode (P02/SBT0 output mode).
• If necessary, set bit 2 of the port 0 pull-up resistor control register
(P0PLU) to add the pull-up resistor.
When the clock source is an external clock (SBT0 pin input):
• Set bit 2 of the P0DIR register to the input mode.
• If necessary, set bit 2 of the P0PLU register.
(7) Select the SC0IOM flag of the SC0MD3 register.
(8) Select serial communication by setting the SC0SBIS flag of the SC0MD3
register to "1." (Reception data wait.)
(9) When the serial reception begins, the SC0BSY flag of the serial interface 0
control register (SC0CTR) is set to "1," indicating that a serial transfer is in
progress.
(10) When the serial reception is complete, the SC0BSY flag of the SC0CTR
register is cleared to "0" and the SC0 transfer complete interrupt request flag
is set to "1." The SC0TRI flag of the SC0MD1 register is set to "1."
Synchronous Serial Interface
When the serial port is enabled
and the SC0CE1 to 0 flags of
the SC0MD0 register are
changed, the transfer bit count
in the SC0LNG2 to 0 flags of
the SC0MD0 register may by
incremented.
[☞ Section 5-2-3, "Serial
Interface Transfer Timing"]
If the start condition is enabled,
the SC0LNG2 to 0 flags of the
SC0MD0 register will be
cleared when the start
condition is received. In this
case, the receive bit count is
fixed at 8 bits.
The SC0SBTS flag of the
SC0MD3 register must be set
to "1" before setting the
SC0SBIS flag of the SC0MD3
register to "1."
If the internal clock is selected
as the clock source, after
setting the SC0SBIS flag of the
SC0MD3 register to "1," write
dummy data to the SC0TRB
register. If there is to be
another reception, write
dummy data again to the
SC0TRB register.
The SC0LNG2 to 0 flags
change at the opposite edge of
the transmit data output edge.
Serial interface 0 begins
operation when the SC0SBOS
flag or the SC0SBIS flag is set
to "1." Set the SC0SBOS flag
or the SC0SBIS flag after all
conditions have been set.
After the transfer is complete, the transfer bit count in the
SC0LNG2 to 0 flags of the SC0MD0 register will be
changed. Except in an 8-bit transfer count, reset the
transfer bit count at the time of the next reception.
When switching from reception to transmission, set the
SC0SBIS flag of the SC0MD3 register to "0" and then set
the SC0SBOS flag to "1." Do not change both of these
flags at the same time.