M30620FCAFP#D5 Renesas Electronics America, M30620FCAFP#D5 Datasheet - Page 613

• Manufacturer Part Number: M30620FCAFP#D5
• Description: IC M16C MCU FLASH 128K 100LQFP
• Manufacturer: Renesas Electronics America
• Series: M16C™ M16C/60r

Specifications of M30620FCAFP#D5

• Core Processor: M16C/60
• Core Size: 16-Bit
• Speed: 16MHz
• Connectivity: SIO, UART/USART
• Peripherals: DMA, PWM, WDT
• Number Of I /o: 85
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: FLASH
• Ram Size: 10K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 10x10b, D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 100-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

Appendix 5
2-294
1.6 Providing of watchdog timer function by software
Figure 1.6.1. Watchdog timer by software
If a microcomputer runs away because of noise or others, it can be detected by a software watchdog timer
and the microcomputer can be reset to normal operation. This is equal to or more effective than program
runaway detection by a hardware watchdog timer. The following shows an example of a watchdog timer
provided by software.
In the following example, to reset a microcomputer to normal operation, the main routine detects errors of
the interrupt processing routine and the interrupt processing routine detects errors of the main routine.
This example assumes that interrupt processing is repeated multiple times in a single main routine process-
ing.
<The main routine>
<The interrupt processing routine>
• Assigns a single byte of RAM to a software watchdog timer (SWDT) and writes the initial value N in the
SWDT once at each execution of the main routine. The initial value N should satisfy the following condi-
tion:
N+1
As the main routine execution cycle may change because of an interrupt processing or others, the initial
value N should have a margin.
• Watches the operation of the interrupt processing routine by comparing the SWDT contents with counts
of interrupt processing after the initial value N has been set.
• Detects that the interrupt processing routine has failed and determines to branch to the program initial-
ization routine for recovery processing in the following case:
If the SWDT contents do not change after interrupt processing.
• Decrements the SWDT contents by 1 at each interrupt processing.
• Determines that the main routine operates normally when the SWDT contents are reset to the initial
value N at almost fixed cycles (at the fixed interrupt processing count).
• Detects that the main routine has failed and determines to branch to the program initialization routine for
recovery processing in the following case:
If the SWDT contents are not initialized to the initial value N but continued to decrement and if they reach
0 or less.
(Counts of interrupt processing executed in each main routine)
N
Interrupt processing
Main processing
(SWDT)
routine errors
Main routine
(SWDT)
FSET I
=N?
=N
N
Interrupt processing routine
(SWDT)
Interrupt processing
Main routine
(SWDT)
errors
0?
(SWDT) – 1
0
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Return
REIT
0
M16C / 62A Group
Mitsubishi microcomputers