R5F21257SNFP#U0 Renesas Electronics America, R5F21257SNFP#U0 Datasheet - Page 101

• Manufacturer Part Number: R5F21257SNFP#U0
• Description: IC R8C/25 MCU FLASH 52LQFP
• Manufacturer: Renesas Electronics America
• Series: R8C/2x/25r

Specifications of R5F21257SNFP#U0

• Core Processor: R8C
• Core Size: 16/32-Bit
• Speed: 20MHz
• Connectivity: I²C, LIN, SIO, SSU, UART/USART
• Peripherals: POR, Voltage Detect, WDT
• Number Of I /o: 41
• Program Memory Size: 48KB (48K x 8)
• Program Memory Type: FLASH
• Ram Size: 2.5K x 8
• Voltage - Supply (vcc/vdd): 2.2 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 52-LQFP
• For Use With: R0K521256S000BE - KIT EVAL STARTER FOR R8C/25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

R8C/24 Group, R8C/25 Group
Rev.3.00
REJ09B0244-0300
The clocks generated by the clock generation circuits are described below.
10.1
Figure 10.10
This clock is supplied by the XIN clock oscillation circuit. This clock is used as the clock source for the CPU and
peripheral function clocks. The XIN clock oscillation circuit is configured by connecting a resonator between the
XIN and XOUT pins. The XIN clock oscillation circuit includes an on-chip feedback resistor, which is
disconnected from the oscillation circuit in stop mode in order to reduce the amount of power consumed by the
chip. The XIN clock oscillation circuit may also be configured by feeding an externally generated clock to the XIN
pin.
Figure 10.10 shows Examples of XIN Clock Connection Circuit.
In reset and after reset, the XIN clock stops.
The XIN clock starts oscillating when the CM05 bit in the CM0 register is set to 0 (XIN clock oscillates) after
setting the CM13 bit in the CM1 register to 1 (XIN- XOUT pin).
To use the XIN clock for the CPU clock source, set the OCD2 bit in the OCD register to 0 (select XIN clock) after
the XIN clock is oscillating stably.
The power consumption can be reduced by setting the CM05 bit in the CM0 register to 1 (XIN clock stops) if the
OCD2 bit is set to 1 (select on-chip oscillator clock).
When an external clock is input to the XIN pin are input, the XIN clock does not stop if the CM05 bit is set to 1. If
necessary, use an external circuit to stop the clock.
In stop mode, all clocks including the XIN clock stop. Refer to 10.5 Power Control for details.
XIN Clock
Feb 29, 2008
NOTE:
Ceramic resonator external circuit
1. Insert a damping resistor if required. The resistance will vary depending on the oscillator and the
(on-chip feedback resistor)
oscillation drive capacity setting. Use the value recommended by the manufacturer of the oscillator.
Use high drive when oscillation starts and, if it is necessary to switch the oscillation drive capacity, do so
after oscillation stabilizes.
When the oscillation drive capacity is set to low, check that oscillation is stable. Also, if the oscillator
manufacturer's data sheet specifies that a feedback resistor be added to the chip externally, insert a
feedback resistor between XIN and XOUT following the instructions.
To use this MCU with supply voltage below VCC = 2.7 V, it is recommended to set the CM11 bit in the
CM1 register to 1 (on-chip feedback resistor disabled), the CM15 bit to 1 (high drive capacity), and
connect the feedback resistor to the chip externally.
XIN
Examples of XIN Clock Connection Circuit
CIN
MCU
Rf
Page 82 of 485
(1)
XOUT
Rd
COUT
(1)
VCC
VSS
Externally derived clock
External clock input circuit
(on-chip feedback resistor)
XIN
MCU
10. Clock Generation Circuit
XOUT
Open