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System Address Mapping Registers
élanSC520 Microcontroller Register Set Manual
2-3
Programming Notes
When the élanSC520 microcontroller comes out of reset, the internal RTC and UARTs are enabled. If the system
application requires the use of an external RTC or UARTs, the internal devices should be disabled during the boot
process and initialization to prevent potential conflicts.
When the integrated UARTs are disabled, only the I/O space accesses associated with these peripherals are
forwarded externally. The accesses to the MMCR registers for the UARTs are not forwarded externally because
these registers are specific to the integrated peripherals. Therefore, the UART MMCR registers should not be used
while the integrated UARTs are disabled.
Even if the internal RTC or UARTs are disabled, setting the IO_HOLE_DEST bit does
not
redirect accesses to the
disabled peripherals to PCI bus I/O space.
2
RTC_DIS
RTC Disable
This bit causes the integrated RTC to be disabled.
0 =The integrated RTC is enabled.
1 =The integrated RTC is not used, and accesses to the RTC address space are forwarded
externally to the GP bus.
When the internal RTC is disabled, the corresponding interrupt request is not automatically
disconnected from the PIC. If an external RTC is to drive the RTC interrupt request, then all
interrupt enables in the RTCCTLB register must be cleared prior to disabling the internal RTC
(see page 17-16).
After the internal RTC is disabled, a PARx window can be defined to target a GPCSx chip
select in the RTC I/O address space. If a PARx window is not used, the external RTC must
fully decode the addresses.
1
UART2_DIS
UART 2 Disable
This bit causes the integrated UART 2 to be disabled.
0 =The integrated UART 2 is enabled.
1 =The integrated UART 2 is not used, and accesses to the UART 2 I/O address space are
forwarded externally to the GP bus.
When the internal UART 2 is disabled, the corresponding interrupt request is not
automatically disconnected from the PIC. If an external UART is to drive the UART 2 interrupt
request, then all interrupt enables in the UART2CTL and UART2INTENB registers must be
cleared (see page 18-3 and page 18-11).
After the internal UART 2 is disabled, a PARx window can be defined to target a GPCSx chip
select in the UART 2 I/O address space. If a PARx window is not used, the external UART
must fully decode the addresses.
0
UART1_DIS
UART 1 Disable
This bit causes the integrated UART 1 to be disabled.
0 =The integrated UART 1 is enabled.
1 =The integrated UART 1 is not used, and accesses to the UART 1 I/O address space are
forwarded externally to the GP bus.
When the internal UART 1 is disabled, the corresponding interrupt request is not
automatically disconnected from the PIC. If an external UART is to drive the UART 1 interrupt
request, then all interrupt enables in the UART1CTL and UART1INTENB registers must be
cleared (see page 18-3 and page 18-11).
After the internal UART 1 is disabled, a PARx window can be defined to target a GPCSx chip
select in the UART 1 I/O address space. If a PARx window is not used, the external UART
must fully decode the addresses.
Bit
Name
Function