Maxim Integrated 71M6521BE Energy Meter IC Family Software - Manual (Page 127)

71M652X Software User’s Guide
Revision 1.7 TERIDIAN Proprietary 127 of 138
© Copyright 2005-2007 TERIDIAN Semiconductor Corporation
Refreshing the WD Timer
The watchdog timer must be refreshed regularly to prevent the reset request signal from becoming active. This re-
quirement imposes an obligation on the programmer to issue two instructions. The first instruction sets WDT and the
second instruction sets SWDT. The maximum delay allowed between setting WDT and SWDT is 12 clock cycles. If this
period has expired and SWDT has not been set, WDT is automatically reset, otherwise the watchdog timer is reloaded
with the content of the WDTREL register and WDT is automatically reset.
Special Function Registers for the WD Timer
Interrupt Enable 0 Register (IEN0):
MSB LSB
EALl WDT ET2 ES0 ET1 EX1 ET0 EX0
Table 6-33: The IEN0 Register
Bit Symbol Function
IEN0.6 WDT Watchdog timer refresh flag.
Set to initiate a refresh of the watchdog timer. Must be set directly before SWDT is
set to prevent an unintentional refresh of the watchdog timer. WDT is reset by
hardware 12 clock cycles after it has been set.
Table 6-34: The IEN0 Bit Functions
Note: The remaining bits in the IEN0 register are not used for watchdog control
Interrupt Enable 1 Register (IEN1):
MSB LSB
EXEN2 SWDT EX6 EX5 EX4 EX3 EX2
Table 6-35: The IEN1 Register
Bit Symbol Function
IEN1.6 SWDT Watchdog timer start/refresh flag.
Set to activate/refresh the watchdog timer. When directly set after setting WDT, a
watchdog timer refresh is performed. Bit SWDT is reset by the hardware 12 clock
cycles after it has been set.
Table 6-36: The IEN1 Bit Functions
Note: The remaining bits in the IEN1 register are not used for watchdog control
Interrupt Priority 0 Register (IP0):
MSB LSB
OWDS WDTS IP0.5 IP0.4 IP0.3 IP0.2 IP0.1 IP0.0
Table 6-37: The IP0 Register
Bit Symbol Function