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μ
PD17016, 17017
115
12.2 Standby Function
The standby function reduces the current consumption of the device by stopping some or all the operations
of the device.
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 oscillation circuit.
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 12.3 explains how to set the operation mode of the device by using the CE pin.
Sections 12.4 and 12.5 respectively explain the halt and clock stop modes.
12.3 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
12.3.1 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
0
and EO
1
pins are floated.
The PLL frequency synthesizer can be disabled by program at any time when the CE pin is high.
12.3.2 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.
12.3.3 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
13. RESET
.