r5f21346mnfp Renesas Electronics Corporation., r5f21346mnfp Datasheet - Page 545

• Manufacturer Part Number: r5f21346mnfp
• Description: Single-chip Mcus Incorporates The R8c Cpu Core
• Manufacturer: Renesas Electronics Corporation.

R8C/34M Group
R01UH0131EJ0100 Rev.1.00
Jun 21, 2011
Figure 25.5
25.4.2
Figure 25.5 shows an Example of Synchronous Serial Communication Unit Operation for Data Transmission
(Clock Synchronous Communication Mode, 8-Bit SSU Data Transfer Length). During data transmission, the
synchronous serial communication unit operates as described below (The data transfer length can be set from 8
to 16 bits using the SSBR register).
When synchronous serial communication unit is set as a master device, it outputs a synchronous clock and data.
When synchronous serial communication unit is set as a slave device, it outputs data synchronized with the
input clock.
When the TE bit is set to 1 (transmit enabled) before writing the transmit data to the SSTDR register, the TDRE
bit is automatically set to 0 (data not transferred from registers SSTDR to SSTRSR) and the data is transferred
from registers SSTDR to SSTRSR.
After the TDRE bit is set to 1 (data transferred from registers SSTDR to SSTRSR), transmission starts. When
the TIE bit in the SSER register is set to 1, the TXI interrupt request is generated. When one frame of data is
transferred while the TDRE bit is set to 0, data is transferred from registers SSTDR to SSTRSR and
transmission of the next frame is started. If the 8th bit is transmitted while the TDRE bit is set to 1, the TEND
bit in the SSSR register is set to 1 (the TDRE bit is set to 1 when the last bit of the transmit data is transmitted)
and the state is retained. The TEI interrupt request is generated when the TEIE bit in the SSER register is set to
1 (transmit-end interrupt request enabled). The SSCK pin is fixed “H” after transmit-end.
Transmission cannot be performed while the ORER bit in the SSSR register is set to 1 (overrun error). Confirm
that the ORER bit is set to 0 before transmission.
Figure 25.6 shows a Sample Flowchart of Data Transmission (Clock Synchronous Communication Mode).
TDRE bit in
SSSR register
TEND bit in
SSSR register
Data Transmission
• SSUMS = 0 (clock synchronous communication mode), CPHS = 0 (data change at
Processing
by program
odd numbers), CPOS = 0 (“H” when clock stops), and BS3 to BS0 = 1000b (8 bits)
Example of Synchronous Serial Communication Unit Operation for Data Transmission
(Clock Synchronous Communication Mode, 8-Bit SSU Data Transfer Length)
SSCK
SSO
Write data to SSTDR register
TXI interrupt request generation
b0
b1
1 frame
25. Synchronous Serial Communication Unit (SSU)
b7
b0
TEI interrupt request
generation
BS0 to BS3: Bits in SSBR register
CPHS, CPOS: Bits in SSMR register
SSUMS: Bit in SSMR2 register
b1
1 frame
b7
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