ST7LITEU09 STMicroelectronics, ST7LITEU09 Datasheet - Page 56

• Manufacturer Part Number: ST7LITEU09
• Description: ST7ULTRALITE - 8-BIT MCU WITH 2K SINGLE VOLTAGE FLASH MEMORY, ADC, TIMERS
• Manufacturer: STMicroelectronics

Specifications of ST7LITEU09

• 2k Bytes Single Voltage Flash Program Memory With Read-out Protection, In-circuit And In-application Programming (icp And Iap). 10k Write/erase Cycles Guaranteed, Data Retention: 20 years at 55°C
• 128 Bytes Data Eeprom. 300k Write/erase Cycles Guaranteed, Data Retention: 20 years at 55°C
• Clock Sources: internal trimmable 8MHz RC oscillator, internal low power, low frequency RC oscillator or external clock
• Five Power Saving Modes: Halt, Auto Wake Up from Halt, Active-Halt, Wait and Slow
• One 8-bit Lite Timer (lt) With Prescaler Including: watchdog, 1 realtime base and 1 input capture

Power saving modes
9.5
56/139
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Auto-wakeup from Halt mode
Auto-wake up from Halt (AWUFH) mode is similar to Halt mode with the addition of a
specific internal RC oscillator for wakeup (Auto-wakeup from Halt oscillator) which replaces
the main clock which was active before entering Halt mode. Compared to Active-halt mode,
AWUFH has lower power consumption (the main clock is not kept running), but there is no
accurate realtime clock available.
It is entered by executing the HALT instruction when the AWUEN bit in the AWUCSR
register has been set.
Figure 29. AWUFH mode block diagram
As soon as Halt mode is entered, and if the AWUEN bit has been set in the AWUCSR
register, the AWU RC oscillator provides a clock signal (f
a fixed divider and a programmable prescaler controlled by the AWUPR register. The output
of this prescaler provides the delay time. When the delay has elapsed, the following actions
are performed:
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After this start-up delay, the CPU resumes operation by servicing the AWUFH interrupt. The
AWU flag and its associated interrupt are cleared by software reading the AWUCSR
register.
To compensate for any frequency dispersion of the AWU RC oscillator, it can be calibrated
by measuring the clock frequency f
Measurement mode is enabled by setting the AWUM bit in the AWUCSR register in Run
instruction. The main reason for this is that the I/O may be wrongly configured due to
external interference or by an unforeseen logical condition.
For the same reason, reinitialize the level sensitiveness of each external interrupt as a
precautionary measure.
The opcode for the HALT instruction is 0x8E. To avoid an unexpected HALT instruction
due to a program counter failure, it is advised to clear all occurrences of the data value
0x8E from memory. For example, avoid defining a constant in ROM with the value
0x8E.
As the HALT instruction clears the I bit in the CC register to allow interrupts, the user
may choose to clear all pending interrupt bits before executing the HALT instruction.
This avoids entering other peripheral interrupt routines after executing the external
interrupt routine corresponding to the wakeup event (reset or external interrupt).
the AWUF flag is set by hardware,
an interrupt wakes-up the MCU from Halt mode,
the main oscillator is immediately turned on and the 256 or 512 CPU cycle delay is
used to stabilize it.
f
AWU_RC
AWU RC
oscillator
divider
/64
AWU_RC
prescaler/1 .. 255
to 8-bit Timer input capture
AWUFH
and then calculating the right prescaler value.
(ei0 source)
AWUFH
interrupt
AWU_RC
). Its frequency is divided by
ST7LITEU05 ST7LITEU09