User`s manual

Am186™CC Microcontroller Router Reference Design User’s Manual
2-30
RESCON Configuration
NOTE:
See sheet 10 in the schematics for RESCON information.
The Reset Configuration (RESCON) register (located in the Am186CC
microcontroller) provides a way to make design-specific hardware configuration
information available to software. The RESCON register is read from AD15-AD0
after a reset. AD15 corresponds to bit 15 of the RESCON register and AD0
corresponds to bit 0. Software can read the value of the RESCON register to
determine the configuration information. Because the Am186CC microcontroller
has weak internal pulldowns, the default value is logic Low. Setting a bit requires
a 10-k
Ω
pullup resistor to VCC5.
Figure 2-5. RESCON Register
• Bit 15 is the Validation Board Bit. A reference design has its own bit, since it
may be used to develop code for other targets and behave as those target boards.
• Bits 14, 13, 12 are the Board ID Bits. They form a unique board identifier to
determine what features are available to the software (USB, POTS, ISDN S/T,
ISDN U, PCnet). D12 is populated by R93 (at location L-7) to provide the
Router Reference Design ID (001 binary).
• Bit 11 is 0 and reserved for future use.
• Bits 10-9 are the Board Revision Bits. They identify unique board revisions
where modifications made to the board may impact software. Bit D9 is populated
by R95 (at location L-7).
• Bit 8 is the Panic Bit. It can be used by software to boot in a safe mode. For
example, software might allow the user to configure a certain board function. If
the user sets this function incorrectly, the user can then set the Panic Bit on the
board to signal software to come up in a valid configuration. No resistor is
installed.
ch2.fm Page 30 Wednesday, July 21, 1999 3:44 PM