PD17012_15 Datasheet, PDF (254/320 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DIGITAL TUNING SYSTEM HARDWARE

µPD17012, 17P012
21.2 Standby Function
The standby function reduces the current consumption of the device by stopping some or all its operations.
The standby function can be used in two modes: halt and clock stop.
The halt mode is to reduce the current consumption of the device by executing a dedicated instruction “HALT
h” and stopping the operation of the CPU.
The clock stop mode is to reduce the current consumption of the device by executing a dedicated instruction
“STOP s” and stopping the 4.5 MHz crystal oscillator.
In addition to the halt and clock stop modes, the operation mode of the device can be also set by the CE pin.
The CE pin is used to control the operation of the PLL frequency synthesizer and reset the device, and can
be said to be a type of the standby function in that it controls the operation of the PLL frequency synthesizer.
The following section 21.3 explains how to set the operation mode of the device by using the CE pin.
Sections 21.4 and 21.5 explain the halt and clock stop modes respectively.
21.3 Selecting Device Operation Mode with CE Pin
The CE pin controls the following functions (1) through (3) by using the level and rising edge of an externally
input signal.
(1) Controls operation of PLL frequency synthesizer
(2) Enables or disables clock stop instruction
(3) Resets device
21.3.1 Controlling operation of PLL frequency synthesizer
The PLL frequency synthesizer can operate only when the CE pin is high.
The PLL frequency synthesizer is automatically disabled when the CE pin is low.
At this time, the VCOH and VCOL pins are internally pulled down, and the EO pin is floated.
The PLL frequency synthesizer can be disabled by the PLL reference clock select register at any time when
the CE pin is high.
21.3.2 Enabling and disabling clock stop instruction
The clock stop instruction “STOP s” is enabled only when the CE pin is low.
The STOP s instruction is executed as a no-operation (NOP) instruction if it is executed when the CE pin is
high.
21.3.3 Resetting device
The device can be reset (CE reset) by raising the CE pin.
The device can also be reset through power application (power-on reset).
For details, refer to 22. RESET.
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Data Sheet U10101EJ4V0DS