HT95R25 Datasheet, PDF (28/51 Pages) Holtek Semiconductor Inc – Phone 8-bit MCU

HT95R25
Register Reset (Power-on)
RES Reset
(Normal/Green)
MODE
000- ---- 00u- ----
MFIC
-000 -000 -000 -000
PFDC
0000 ---- 0000 ----
PFDD
0000 0000 0000 0000
Note:
²u² stands for unchanged
²x² stands for unknown
²-² stands for unimplemented
RES Reset
(Sleep/Idle)
00u- ----
-000 -000
0000 ----
0000 0000
WDT Time-out
(Normal/Green)
00u- ----
-000 -000
0000 ----
0000 0000
WDT Time-out
(Sleep/Idle)
00u- ----
-uuu -uuu
uuuu ----
uuuu uuuu
Oscillator
There are two oscillator circuits within the controller.
One is for the system clock which uses an externally
connected 32768Hz crystal. The other is an internal
watchdog oscillator.
System Crystal/Ceramic Oscillator
The system clock is generated using an external
32768Hz crystal or ceramic resonator connected be-
tween pins X1 and X2. From this clock source an inter-
nal circuit generates a 3.58MHz clock source which is
also required by the system. This frequency generator
circuit requires the addition of externally connected RC
components to pin XC to form a low pass filter for the
3.58MHz output frequency stabilisation.
X1
X2
15kW
XC
3nF
47nF
Crystal/Ceramic Oscillator
Watchdog Timer Oscillator
The WDT oscillator is a fully integrated free running RC
oscillator with a typical period of 65ms at 5V, requiring no
external components. It is selected via configuration op-
tion. If selected, when the device enters the Power
Down Mode, the system clock will stop running, how-
ever the WDT oscillator will continue to run and keep the
watchdog function active. However, as the WDT will
consume a certain amount of power when in the Power
Down Mode, for low power applications, it may be desir-
able to disable the WDT oscillator by configuration op-
tion.
Operation Mode, Power-down and
Wake-up
There are four operational modes, known as the idle
mode, sleep mode, green mode, and normal mode. The
chosen mode is selected using the MODE0, MODE1
and UPEN bits in the PFDC register but also depends
upon whether the HALT instruction has been executed
or not.
Idle Mode
When the device enters this mode, the normal operating
current, will be reduced to an extremely low standby cur-
rent level. This occurs because when the device enters
the Power Down Mode, both the 3.58MHz and 32768Hz
system oscillators are stopped which reduces the power
consumption to extremely low levels, however, as the
device maintains its present internal condition, it can be
woken up at a later stage and continue running, without
requiring a full reset. This feature is extremely important
in application areas where the microcontroller must
have its power supply constantly maintained to keep the
device in a known condition but where the power supply
capacity is limited such as in battery applications.
HALT
Instruction
Not executed
Not executed
Executed
Executed
MODE1
1
0
0
0
MODE0
X
X
0
1
UPEN
1
0
0
0
Operation
Mode
Normal
Green
Sleep
Idle
32768Hz
ON
ON
ON
OFF
Note: ²X² means don¢t care
MODE0 will be cleared to 0 automatically after wake-up from Idle Mode.
3.58MHz
ON
OFF
OFF
OFF
System
Clock
3.58MHz
32768Hz
Stopped
Stopped
Rev. 1.00
28
March 6, 2009