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10
Startup Configuration and Bootstrap Loading
After start-up, the XC2200 executes code out of an on-chip or off-chip program memory.
The initial code source can be selected via hardware configuration (i.e. defined levels on
specific pins):
•
Internal Start
Mode: executes code out of the on-chip program Flash.
•
External Start
External Bus Interface.
•
Bootstrap Loading
(PSRAM). This code is downloaded beforehand via a selectable serial interface.
10.1
Start-Up Mode Selection
After any start-up the currently valid start-up configuration is indicated in bitfield HWCFG
of register SCU_STSTAT.
A start-up configuration can be selected in two ways:
1. Via an externally applied hardware configuration upon a Power-on or Internal
Application reset
The hardware configuration is applied to Port 10 pins (P10.[3:0]).
The hardware that activates a startup configuration during reset may be simple pull
resistors for systems that use this feature upon every reset. You may want to use a
switchable solution (via jumpers or an external signal) for systems that only
temporarily use a hardware configuration.
2. By executing the following software sequence (using SCU_SWRSTCON and
SCU_RSTCON1 registers):
a) Write
respective
SCU_SWRSTCON.SWCFG;
b) Assign desired type of reset to the software request trigger by writing into
SCU_RSTCON1.SW bitfield (by default SCU_RSTCON1.SW=00
reset generated by software request trigger)
c) Set Software Boot Configuration bit: SCU_SWRSTCON.SWBOOT = 1;
d) Trigger
a
SCU_SWRSTCON.SWRSTREQ = 1.
There is a differentiation of XC2200 behavior in case of Application reset which must be
noted:
•
an Application reset triggered by hardware request (for example WDT, ESRx) does
not cause evaluation of the P10 pins - the same start-up configuration is used as after
the previous reset;
•
an
Application
SCU_SWRSTCON.SWRSTREQ=1) can have different consequences:
– if Software Boot Configuration is selected (SCU_SWRSTCON.SWBOOT=1) - the
start-up configuration is updated from SCU_SWRSTCON.SWCFG bitfield;
User's Manual
SCFG/BSL, V1.3
Mode: executes code out of an off-chip memory connected to the
Modes: execute code out of the on-chip program SRAM
Table 10-1
configuration
software
reset
reset
triggered
Startup Configuration and Bootstrap Loading
summarizes the defined start up modes.
value
(refer
by
activating
by
10-1
XC2200 Derivatives
System Units (Vol. 1 of 2)
to
Table
10-1)
meaning no
B
Software
Reset
software
(with
V2.1, 2008-08
to
bitfield
Request:
setting
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