ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 86

• Manufacturer Part Number: ade7566
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ADE7566/ADE7569
Writing to the Watchdog Timer SFR (WDCON, 0xC0)
Writing data to the WDCON SFR involves a double instruction sequence. The WDWR bit must be set and the following instruction must
be a write instruction to the WDCON SFR.
Disable Watch dog
CLR EA
SETB WDWR
CLR WDE
SETB EA
This sequence is necessary to protect the WDCON SFR from code execution upsets that may unintentionally modify this SFR. Interrupts
should be disabled during this operation due to the consecutive instruction cycles.
Table 74. Watchdog and Flash Protection Byte in Flash (Flash Address = 0x3FFA)
Bit No.
7
7 to 0
Watchdog Timer Interrupt
If the watchdog timer is not cleared within the watchdog timeout
period, a system reset occurs unless the watchdog timer interrupt
is enabled. The watchdog timer interrupt enable bit (WDIR) is
located in the Watchdog Timer SFR (WDCON, 0xC0). Enabling
the WDIR bit allows the program to examine the stack or other
variables that may have led the program to execute inappropriate
Mnemonic
WDPROT_PROTKY7
PROTKY[7:0]
Default
1
0xFF
Description
This bit holds the protection for the watchdog timer and the 7
When this bit is cleared, the watchdog enable and event, selected by WDE and WDIR cannot be
changed by user code. The watchdog configuration is then fixed to WDIR = 0 and WDE = 1. The
watchdog timeout in PRE[3:0] can still be modified by user code.
The value of this bit is also used to set the flash protection key. If this bit is cleared to protect the
watchdog, then the default value for the flash protection key is 0x7F instead of 0xFF (see the
Protecting the Flash Memory section for more information on how to clear this bit).
These bits hold the flash protection key. The content of this flash address is compared to the
Flash Protection Key SFR (PROTKY, 0xBB) when the protection is being set or changed. If the two
values match, the new protection is written to the flash Address 0x3FFF to Address 0x3FFB. See
the Protecting the Flash Memory section for more information on how to configure these bits.
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code. The watchdog timer interrupt also allows the watchdog to
be used as a long interval timer.
Note that WDIR is automatically configured as a high priority
interrupt. This interrupt cannot be disabled by the EA bit in the
IE register (see Table 66). Even if all of the other interrupts are
disabled, the watchdog is kept active to watch over the program.
th
bit of the flash protection key.