ST10F269 Datasheet, PDF (110/160 Pages) STMicroelectronics – 16-BIT MCU WITH MAC UNIT, 256K BYTE FLASH MEMORY AND 12K BYTE RAM

ST10F269
The short hardware reset ends and the MCU restarts.To be processed as a short hardware reset, the
external RSTIN signal must last a maximum of 1038 TCL (4 TCL + 10 TCL + 1024 TCL). The system
configuration is latched from PORT0 after a duration of 8 TCL / 4 CPU clocks (6 TCL / 3 CPU clocks if PLL
is bypassed) and in case of external fetch, ALE, RD and R/W pins are driven to their inactive level.
Program execution starts from memory location 00'0000h in code segment 0. This starting location will
typically point to the general initialization routine. Timings of synchronous reset sequence are
summarized in Figure 57. Refer to Table 29 for PORT0 latched configuration.
Note - If the RSTIN pin level is sampled low, the reset sequence is extended until RSTIN level becomes
high leading to a long hardware reset (synchronous or asynchronous reset) because RSTIN
signal duration has lasted longer than 1040TCL.
- If the V_RPD voltage has droped below the RPD pin threshold, the reset is processed as an
asynchronous reset.
Figure 57 : Synchronous Warm Reset Sequence External Fetch (4 TCL < RSTIN pulse < 1038 TCL)
CPU Clock
RSTIN
RPD
RSTOUT
ALE
4 TCL 10 TCL ²⁾
min. min.
1)
200µA Discharge
1024 TCL
6 or 8 TCL⁴⁾
1 23456789
Internally pulled low ³⁾
If V_RPD > 2.5V Asynchronous
Reset is not entered.⁵⁾
5 TCL
RD
PORT0
Internal reset signal
Reset Configuration
1st Instr.
Latching point of PORT0
for system start-up configuration
Note
1) RSTIN assertion can be released there.
2) Maximum internal synchronisation is 6 CPU cycles (12 TCL).
3) RSTIN pin is pulled low if bit BDRSTEN (bit 3 of SYSCON register) was previously set by software. Bit BDRSTEN is cleared after
reset.
4) RSTIN rising edge to internal latch of PORT0 is 3 CPU clock cycles (6 TCL) if the PLL is bypassed and the prescaler is on
(f_CPU = f_XTAL / 2), else it is 4 CPU clock cycles (8 TCL).
5) If during the reset condition (RSTIN low), V_RPD voltage drops below the threshold voltage (typically 2.5V for 5V operation), the
ST10 reset circuitry disables the bidirectional reset function and RSTIN pin is no more pulled low.
18.3 - Software Reset
The reset sequence can be triggered at any time using the protected instruction SRST (software reset).
This instruction can be executed deliberately within a program, for example to leave bootstrap loader
mode, or upon a hardware trap that reveals a system failure.
Upon execution of the SRST instruction, the internal reset sequence (1024 TCL) is started. The
microcontroller behavior is the same as for a short hardware reset, except that only P0.12...P0.6 bits are
latched at the end of the reset sequence, while previously latched values of P0.5...P0.2 are cleared.
18.4 - Watchdog Timer Reset
When the watchdog timer is not disabled during the initialization or when it is not regularly serviced during
program execution it will overflow and it will trigger the reset sequence.
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