301
μ
PD17704, 17705, 17707, 17708, 17709
20.4 Device Operation in Halt and Clock Stop Status
Table 20-1 shows the operations of the CPU and peripheral hardware units in the halt and clock stop status.
In the halt status, all the peripheral hardware units continue the normal operation until instruction execution is
stopped.
In the clock stop status, all the peripheral hardware units stop operation.
The control registers that control the operations of the peripheral hardware units operate normally (not initialized)
in the halt status, but are initialized to specified values when the clock stop instruction is executed.
In other words, all peripheral hardware continues the operation specified by the control register in the halt status,
and the operation is determined by the initialized value of the control register in the clock stop status.
For the values of the control registers in the clock stop status, refer to
8. REGISTER FILE (RF)
.
Table 20-1. Device Operation in Halt and Clock Stop Status
Peripheral Hardware
Status
Halt
Clock stop
Program counter
Stops at address of HALT instruction
Stops at address of STOP instruction
System register
Retained
Retained
Peripheral register
Retained
Partly initialized
Note 1
Control register
Retained
Partly initialized
Note 1
Timer
Normal operation
Operation stops
PLL frequency synthesizer
Normal operation
Note 2
Operation stops
A/D converter
Normal operation
Operation stops
D/A converter
Normal operation
Stops operation and used as general-
purpose output port
Serial interface
Stops operation when internal clock (master)
is selected and continues operation when
external clock (slave) is selected
Stops operation and used as general-
purpose I/O port
Frequency counter
Normal operation
Stops operation and used as general-
purpose input port
BEEP output
Normal operation
Stops operation and used as general-
purpose I/O port
General-purpose I/O port
Normal operation
Retained
General-purpose input port
Normal operation
Input port
General-purpose output port
Normal operation
Retains output latch
Notes 1.
For the value to which these registers are initialized, refer to
5. SYSTEM REGISTER (SYSREG)
and
8. REGISTER FILE (RF)
.
2.
The PLL frequency synthesizer is automatically disabled by the low level input to the CE pin.
20.5 Cautions on Processing of Each Pin in Halt and Clock Stop Status
The halt status is used to reduce the current consumption when, say, only the watch is used.
The clock stop function is used to reduce the current consumption of the device to only use the data memory.
Therefore, the current consumption must be reduced as much as possible in the halt status or clock stop status.
At this time, the current consumption significantly varies depending on the status of each pin, and the points shown
in Table 20-2 must be noted.