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Section 4 Clock Pulse Generators
Rev. 6.00 Sep 12, 2006 page 86 of 526
REJ09B0326-0600
In standby mode, watch mode, subactive mode, and subsleep mode, the system clock pulse
generator stops. Prescaler S also stops and is initialized to H'0000.
The CPU cannot read or write prescaler S.
The output from prescaler S is shared by the on-chip peripheral modules. The divider ratio can be
set separately for each on-chip peripheral function.
In active (medium-speed) mode the clock input to prescaler S is determined by the division factor
designated by MA1 and MA0 in SYSCR1.
Prescaler W (PSW):
Prescaler W is a 5-bit counter using a 32.768 kHz signal divided by 4 (
φ
W
/4)
as its input clock.
Prescaler W is initialized to H'00 by a reset, and starts counting on exit from the reset state.
Even in standby mode, watch mode, subactive mode, or subsleep mode, prescaler W continues
functioning so long as clock signals are supplied to pins X
1
and X
2
.
Prescaler W can be reset by setting 1s in bits TMA3 and TMA2 of timer mode register A (TMA).
Output from prescaler W can be used to drive timer A, in which case timer A functions as a time
base for timekeeping.
4.5
Note on Oscillators
Oscillator characteristics are closely related to board design and should be carefully evaluated by
the user, referring to the examples shown in this section. Oscillator circuit constants will differ
depending on the oscillator element, stray capacitance in its interconnecting circuit, and other
factors. Suitable constants should be determined in consultation with the oscillator element
manufacturer. Design the circuit so that the oscillator element never receives voltages exceeding
its maximum rating.
Summary of Contents for F-ZTAT H8/3642A Series
Page 6: ...Rev 6 00 Sep 12 2006 page iv of xx ...
Page 8: ...Rev 6 00 Sep 12 2006 page vi of xx ...
Page 22: ...Rev 6 00 Sep 12 2006 page xx of xx ...
Page 124: ...Section 5 Power Down Modes Rev 6 00 Sep 12 2006 page 102 of 526 REJ09B0326 0600 ...
Page 188: ...Section 6 ROM Rev 6 00 Sep 12 2006 page 166 of 526 REJ09B0326 0600 ...
Page 190: ...Section 7 RAM Rev 6 00 Sep 12 2006 page 168 of 526 REJ09B0326 0600 ...
Page 298: ...Section 9 Timers Rev 6 00 Sep 12 2006 page 276 of 526 REJ09B0326 0600 ...
Page 378: ...Section 12 A D Converter Rev 6 00 Sep 12 2006 page 356 of 526 REJ09B0326 0600 ...
Page 446: ...Section 13 Electrical Characteristics Rev 6 00 Sep 12 2006 page 424 of 526 REJ09B0326 0600 ...