Fujitsu F2MC-8FX MB95200H/210H Series Installation and operating instructions

Fujitsu Microelectronics (Shanghai) Co., Ltd.
Application Note
MCU-AN-500013-E-11
F²MC-8FX FAMILY
8-BIT MICROCONTROLLER
MB95200H/210H SERIES
WATCHDOG TIMER
APPLICATION NOTE

WATCHDOG TIMER V1.1
Revision History
MCU-AN-500013-E-11 – Page 2
Revision History
Date Author Change of Records
2008-03-20 Levi.Zhang V1.0, First Draft
2008-07-18 Levi.Zhang V1.1, Add URL in chapter 6 Additional Information; modify
figure number and some sample code.
This manual contains 19 pages.
© 2008 Fujitsu Microelectronics (Shanghai) Co., Ltd.
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caused by the use of information or drawings described in this manual.
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4. The products contained in this manual are not intended for use with equipments which require extremely
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WATCHDOG TIMER V1.1
Contents
MCU-AN-500013-E-11 – Page 3
Contents
REVISION HISTORY............................................................................................................ 2
CONTENTS.......................................................................................................................... 3
1INTRODUCTION.............................................................................................................. 4
2WATCHDOG TIMER........................................................................................................ 5
2.1Key Features........................................................................................................... 5
2.2Block Diagram......................................................................................................... 5
2.3Registers................................................................................................................. 6
2.3.1Watchdog Timer Control Register (WDTC)................................................ 6
2.3.2Watchdog Timer Selection ID Register (WDTH, WDTL) ............................ 6
2.4NVR (Non-Volatile Register) function ...................................................................... 7
3INTERVAL TIME.............................................................................................................. 8
4USAGE AND EXAMPLES ............................................................................................... 9
4.1Functions and Operations of watchdog timer........................................................... 9
4.2Software watchdog timer....................................................................................... 10
4.3Hardware watchdog timer...................................................................................... 11
5NOTE ON USING WATCHDOG TIMER......................................................................... 12
6ADDITIONAL INFORMATION ....................................................................................... 13
7APPENDIX..................................................................................................................... 14
7.1List of Figures........................................................................................................ 14
7.2List of Tables......................................................................................................... 15
7.3Sample Code ........................................................................................................ 16
7.3.1Project Name: SWWDT ........................................................................... 16
7.3.2Project Name: HWWDT........................................................................... 18

WATCHDOG TIMER V1.1
Chapter 1 Introduction
MCU-AN-500013-E-11 – Page 4
1 Introduction
This application note describes how to use the watch-dog timer.
The application note describes the functions of the watchdog timer and gives some
examples.

WATCHDOG TIMER V1.1
Chapter 2 Watchdog Timer
MCU-AN-500013-E-11 – Page 5
2 Watchdog Timer
Basic function of the watchdog timer
2.1 Key Features
The watchdog timer functions as a counter used to prevent program from running out of
control. Once the watchdog timer is activated, its counter needs to be cleared at specified
intervals regularly. A watchdog reset is generated if the timer is not cleared within a preset
interval time base on chapter 3. The watchdog timer that is not cleared may be due to
problems in the program which has entered into an infinite loop or Stack over-run or other
possible problems that caused the CPU to hang.
The watchdog timer has the following features:
Count clock selector
Watchdog timer counter
Reset control circuit is used to generate the reset signal when the WDT counter
overflows
Watchdog timer clear selector is used to selects the watchdog timer clear signal
Counter timer control circuit
Hardware and software watchdog timer
2.2 Block Diagram
Figure 2-1 shows the internal block diagram of watchdog timer.
Figure 2-1: Block Diagram of Watchdog Timer

WATCHDOG TIMER V1.1
Chapter 2 Watchdog Timer
MCU-AN-500013-E-11 – Page 6
2.3 Registers
Please refer to Chapter 11 and Chapter 22 of MB95200H/210H Series Hardware Manual for
detailed register setting.
2.3.1 Watchdog Timer Control Register (WDTC)
This register is used to activate or clear the watchdog timer.
Address bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 Initial value
000C
H
CS1 CS0 CSP HWWDT WTE3 WTE2 WTE1 WTE0
software R/W R/W R/W R0,WX R0/W R0/W R0/W R0/W 00000000
B
hardware R0/WX R0/WX R1/WX R1,WX R0/W R0/W R0/W R0/W 00110000
B
Figure 2-2: WDTC
2.3.2 Watchdog Timer Selection ID Register (WDTH, WDTL)
The two registers are used to select hardware or software watchdog timer.
Address bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 Initial value
0FEB
H
WDTH WDTH7 WDTH6 WDTH5 WDTH4 WDTH 3 WDTH 2 WDTH 1 WDTH 0 xxxxxxxx
0FEC
H
WDTL WDTL7 WDTL6 WDTL5 WDTL4 WDTL 3 WDTL 2 WDTL 1 WDTL 0 xxxxxxxx
R/WX R/WX R/WX R/WX R/WX R/WX R/WX R/WX
Figure 2-3: Watchdog Timer Selection ID Register (WDTH, WDTL)
R/W: Readable/writeable (Read value is the same as write value)
R/WX: Read only (Readable, writing has no effect on operation)
R0/WX: Undefined bit (Read value is “0”, writing has no effect on operation)
R1/WX: Undefined bit (Read value is “1”, writing has no effect on operation)
R0/W: Write only (Writable, “0” is read)

WATCHDOG TIMER V1.1
Chapter 2 Watchdog Timer
MCU-AN-500013-E-11 – Page 7
2.4 NVR (Non-Volatile Register) function
The NVR interface enables users to select hardware or software watchdog timer by
modifying the 16-bit watchdog timer selection ID. Please note that the watchdog timer
selection ID cannot be modified while the CPU is running, therefore please modify NVR in
Flash Area first, then the MCU will copy these values to NVR interface (IO Area)
automatically after a reset.
Figure 2-4 shows the basic configuration of serial programming connection for flash memory
products.
Figure 2-4: Retrieval of NVR during Reset
Please note that either the SWWDT or HWWDT can work in the same time. NVR is used to
decide which one is working.
These 16 bits of WDTH and WDTL are loaded from the flash address FFBE
H
, FFBF
H
after a
reset. The initial values are determined by the pre-loaded values in the NVR flash area.
Write certain values to the address FFBE
H
and FFBF
H
to select watchdog timer’s mode.
Table 2-1 shows watchdog timer selection ID.
WDTH[7:0], WDTL[7:0] Function
A596
H
The HWWDT is disabled and the SWWDT is enabled.
A597
H
The HWWDT is selected and the SWWDT is disabled. [It can be stopped in one of the standby modes
(stop/sleep/timebase timer/watch mode).]
Other than the above values The WHWDT is selected and the SWWDT is disabled. [It keeps running in one of the standby modes
(stop/sleep/timebase timer/watch mode).]
Table 2-1: Watchdog Timer Selection ID

WATCHDOG TIMER V1.1
Chapter 3 Interval time
MCU-AN-500013-E-11 – Page 8
3 Interval time
This section describes the interval time of the watchdog timer
The interval times of the watchdog timer are shown in Table 3-1. If the counter of watchdog
timer is not cleared, a watchdog reset is generated between the minimum time and the
maximum time.
Count clock type Count clock switch bit
CS[1:0], CSP
Interval time
Minimum time Maximum time
Timebase timer output
(main clock = 4MHz)
000
B
(SWWDT) 2
21
/F
CH
524 ms 1.05 s
010
B
(SWWDT) 2
20
/F
CH
262 ms 524 ms
Watch prescaler output
( sub-clock = 32.768KHz)
100
B
(SWWDT) 2
14
/F
CL
500 ms 1.00 s
110
B
(SWWDT) 2
13
/F
CL
250 ms 500 ms
Sub-CR timer
(sub-CR clock = 50-200KHz)
XX1
B
(SWWDT) or
HWWDT*
1
2
16
/F
CRL
328 ms 2.62 s
*1: CS [1:0] = 00
B
, CSP = 1
B
(read only)
Table 3-1: Interval Times of Watchdog Timer
The interval time varies depending on the timing of clearing the watchdog timer. Figure 3-1
shows the correlation between the timing of clearing the watchdog timer and the interval time
when the timebase timer output 2
21
/F
CH
(F
CH
: main clock) is selected as the count clock
(main clock = 4MHz).
Figure 3-1: Clearing Timing and Interval Time of Watchdog Timer
Please note that program must clear the counter of the watchdog timer within the minimum
time.

WATCHDOG TIMER V1.1
Chapter 4 Usage and Examples
MCU-AN-500013-E-11 – Page 9
4 Usage and Examples
Functions and examples for watchdog timer
This section describes the usage of watchdog timer and gives some examples.
4.1 Functions and Operations of watchdog timer
Please write certain values to NVR flash area address FFBE
H
and FFBF
H
to choose the
watchdog timer operation mode. See Table 2-1 for detailed settings of mode choose.
The Watchdog Timer has two operate modes as below:
Software watchdog
1) Write “A596
H
” (enable software watchdog timer) to the address FFBE
H
and
FFBF
H
on the flash memory, which are copied to the watchdog timer selection
ID register WDTH/WDTL (0FEB
H
/0FEC
H
) after a reset.
2) The watchdog timer is activated when “0101B” is written to the watchdog
control bits of the watchdog timer control register (WDTC: WTE3 to WTE0) for
the first time after a reset. The count clock switch bits of the watchdog timer
register (WDTC: CS1, CS0, CSP) should also be set at the same time.
3) Once the watchdog timer is activated, a reset is the only way to stop its
operation. Please clear watchdog counter in a specified intervals regularly
depend on the setting of WDTC: CS1, CS0, CSP. Refer to Table 3-1 for
detailed interval time.
Hardware watchdog
1) Write “A597
H
” (WDT can be stopped in a standby mode) or any other value
(WDT is enabled in every mode) except than “A596
H
” or “A597
H
” to the
address FFBE
H
and FFBF
H
on the flash memory, which are copied to the
watchdog timer selection ID register WDTH/WDTL (0FEB
H
/0FEC
H
) after a
reset.
2) The hardware watchdog timer starts automatically after a reset and cannot be
stopped. Please clear its counter at specified intervals regularly to avoid
generates a watchdog timer reset.
3) This timer is cleared by reset and resumes operation after the reset.
Please note that the watchdog timer is cleared at the same time as the timer selected as the
count clock (timebase timer or watch prescaler) is cleared. For this reason, the watchdog
timer cannot function as such, if the software is set to clear the selected timer repeatedly
during the interval time of the watchdog timer

WATCHDOG TIMER V1.1
Chapter 4 Usage and Examples
MCU-AN-500013-E-11 – Page 10
4.2 Software watchdog timer
Setting Procedure Example
The software watchdog timer is set up through the following procedure:
1) Ensure that the address FFBE
H
, FFBF
H
values are “A596
H
” (NVR flash area)
2) Select the count clock. (WDTC:CS1,CS0,CSP)
3) Activate the watchdog timer. (WDTC:WTE3 to WTE0 = 0101
B
)
4) Clear the watchdog timer within the minimum interval time. (WDTC:WTE3 to WTE0 =
0101
B
)
Refer Table 3-1.
The following example shows how to set up watchdog Timer for operation with software
mode.
main.c
startup.asm
Refer to Appendix Sample Code for project “SWWDT”.
Please note that once the watchdog timer is activated, it cannot be stopped until a reset is
generated.
/* THIS SAMPLE CODE IS PROVIDED AS IS AND IS SUBJECT TO ALTERATIONS. */
/* FUJITSU MICROELECTRONICS ACCEPTS NO RESPONSIBILITY OR LIABILITY */
/* FOR ANY ERRORS OR ELIGIBILITY FOR ANY PURPOSES. */
/* (C) Fujitsu Microelectronics (Shanghai) Co., LTD. */
/* Date: 20080320 Version: 1V0 Author: Levi */
/*--------------------------------------------------------------------*/
/* initial watchdog timer */
void InitWDT (void)
{
WDTC = 0x05; // set count clock is 2
21
/F
CH
// start WDT counter
}
/* main routine */
void main (void)
{
InitWDT();
...
WDTC |= 0x05; // clear WDT counter
}
#define HWD_DISABLE
;------------------------------------------------------------------------
; Hard Watchdog
;------------------------------------------------------------------------
#ifdef HWD_DISABLE
.SECTION WDT, CONST, LOCATE=H'FFBE
.DATA.W 0xA596
#
endif