ST7LITE49K2 STMicroelectronics, ST7LITE49K2 Datasheet - Page 81

• Manufacturer Part Number: ST7LITE49K2
• Description: 8-bit MCU
• Manufacturer: STMicroelectronics

Specifications of ST7LITE49K2

• 8 Kbytes Single Voltage Extended Flash (xflash) Program Memory With Read-out Protection In-circuit Programming And In-application Programming (icp And Iap) Endurance: 10K write/erase cycles guaranteed Data retention
• 256 Bytes Data Eeprom With Read-out Protection. 300k Write/erase Cycles Guaranteed, Data Retention: 20 years at 55 °C.
• Clock Sources: Internal trimmable 8 MHz RC oscillator, auto-wakeup internal low power - low frequency oscillator, crystal/ceramic resonator or external clock
• Five Power Saving Modes: Halt, Active-halt, Auto-wakeup from Halt, Wait and Slow

ST7LITE49K2
11
11.1
11.1.1
11.1.2
11.1.3
On-chip peripherals
Watchdog timer (WDG)
Introduction
The Watchdog timer is used to detect the occurrence of a software fault, usually generated
by external interference or by unforeseen logical conditions, which causes the application
program to abandon its normal sequence. The Watchdog circuit generates an MCU reset on
expiry of a programmed time period, unless the program refreshes the counter’s contents
before the T6 bit becomes cleared.
Main features
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Functional description
The counter value stored in the CR register (bits T[6:0]), is decremented every 16000
machine cycles, and the length of the timeout period can be programmed by the user in 64
increments.
If the watchdog is activated (the WDGA bit is set) and when the 7-bit timer (bits T[6:0]) rolls
over from 40h to 3Fh (T6 becomes cleared), it initiates a reset cycle pulling low the RESET
pin for typically 30µs.
Figure 36. Watchdog block diagram
Programmable free-running downcounter (64 increments of 16000 CPU cycles)
Programmable reset
Reset (if watchdog activated) when the T6 bit reaches zero
Optional reset on HALT instruction (configurable by option byte)
Hardware Watchdog selectable by option byte
f
CPU
WDGA
RESET
T6
T5
WATCHDOG CONTROL REGISTER (CR)
7-BIT DOWNCOUNTER
CLOCK DIVIDER
T4
÷16000
T3
T2
T1
T0
On-chip peripherals
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