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UM0404 System reset
The following describes the different selections that are offered for reset configuration.
The default modes refer to pins at high level, without external pull-down devices connected.
Emulation mode: P0L.0
When low during reset, pin P0L.0 (EMU) selects the Emulation Mode. This mode allows the
access to integrated XBUS peripherals via the external bus interface pins in application
specific version of the ST10F276. In addition also the RSTOUT
pin floats to tristate rather to
be driven low. When the emulation mode is latched the CLKOUT output is automatically
enabled. This mode is used for special emulator purposes and is not used in basic
ST10F276 devices, so in this case P0L.0 should be held high.
Default: Emulation Mode is off.
Adapt mode: P0L.1
Pin P0L.1 (ADP) selects the Adapt Mode, when low during reset. In this mode the
ST10F276 goes into a passive state, which is similar to its state during reset.
The pins of the ST10F276 float to tristate or are deactivated via internal pull-up/pull-down
devices, as described for the reset state. In addition also the RSTOUT
pin floats to tristate
rather than be driven low, and the on-chip oscillator is switched off.
This mode allows switching a ST10F276 that is mounted to a board virtually off, so an
emulator may control the board’s circuitry, even though the original ST10F276 remains in its
place. The original ST10F276 also may resume to control the board after a reset sequence
with P0L.1 high.
Default: Adapt mode is off.
Note: When XTAL1 is fed by an external clock generator (while XTAL2 is left open), this clock
signal may also be used to drive the emulator device.
However, if a crystal is used, the emulator device’s oscillator can use this crystal only, if at
least XTAL2 of the original device is disconnected from the circuitry (the output XTAL2 will
still be active in Adapt Mode).
Reserved: P0L.2 - P0L.3
These pins must be always left open (or driven high) during reset, to avoid ST10 enters
particular test mode and consequently does not work properly.
Default: Test Modes are off.
Bootstrap loader mode: P0L.4 - P0L.5
Pins P0L.4 and P0L.5 (BSL) activate the on-chip bootstrap loader modes. The bootstrap
loader allows moving the start code into the IRAM of the ST10F276 via the serial interface
ASC0 or CAN1. The MCU will remain in bootstrap loader mode until a hardware reset with
P0L.4 and P0L.5 both high or a software reset occurrence. Refer to Section 15: The
bootstrap loader on page 302 for details.
Default: The ST10F276 starts fetching code from location 00’0000h, the bootstrap loader is
off.
External bus type: P0L.6 - P0L.7
Pins P0L.7 and P0L.6 (BUSTYP) select the external bus type during reset, if an external
start is selected via pin EA
. This allows the configuration of the external bus interface of the
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