Panasonic MN101C00 user manual Serial Functions

■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."

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.

Chapter 5 Serial Functions

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.

Synchronous Serial Interface 97