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System Initialization
3-8
Élan™SC520 Microcontroller User’s Manual
2. If needed, program the PIO pin logic to map the GP bus chip select signal and other
control signals to a physical pin.
3. Program a PAR register to map the external peripheral into physical address space and
to configure a chip select for the device.
For peripherals connected externally to the GP bus, the Programmable Address Region
registers control where they are mapped into the I/O or memory address space.
Programming and using these registers is discussed in Section 3.7.
3.6
CONFIGURING THE PIN MULTIPLEXING
The ÉlanSC520 microcontroller has several pins that are multiplexed to two functions.
There are no pins that have three functions. Most of the pins that are multiplexed are
programmable input/output pins (PIOs).
To program a pin that is multiplexed with a PIO, its corresponding function bit must be set
in the PIO31–PIO16 Pin Function Select (PIOPFS31_16) register (MMCR offset C22h) or
the PIO15–PIO0 Pin Function Select (PIOPFS15_0) register (MMCR offset C20h).
Other pins with multiple programmable functions are all noted in Figure 2-2 on page 2-3.
3.7
CONFIGURING THE PROGRAMMABLE ADDRESS REGION (PAR)
REGISTERS
The PAR registers provide a common programming interface to configure physical memory
and I/O regions in an ÉlanSC520 microcontroller system. PAR registers are programmed
by atomically writing 32-bit values. See “Programmable Address Region (PAR) Registers”
on page 4-5 for more information on using the PAR registers. “Software Considerations”
on page 4-17 provides other important details.
The PAR registers are used to define four characteristics.
■
Target device
■
Attributes for the address region
■
Size of the address region
■
Start address for the region
It is important to note that the PAR registers are used to define
physical address regions.
PAR registers are not used to define effective address regions or linear address regions.
For example, an effective address (often called a logical or virtual address) gets translated
into a linear address by the Am5
x
86 CPU’s segmentation unit. If the paging unit is enabled,
then linear addresses get translated into physical addresses and placed on the CPU’s bus.
If the paging unit is not enabled, then the mapping from linear address to physical address
is direct (one-to-one).
Depending on how your system is set up, driver software, system software and other
software that must be aware of physical addresses should be written to take the Am5
x
86
CPU addressing modes into account. This can be an extremely complex topic and is beyond
the scope of this chapter.
The general format of the PAR registers is shown in Figure 3-2 on page 3-10. Provided as
a programming aid, Figure 3-3 on page 3-11 is a blank worksheet for calculating PAR
register values.
Содержание Elan SC520
Страница 1: ...lan SC520 Microcontroller User s Manual Order 22004A...
Страница 4: ...iv lan SC520 Microcontroller User s Manual...
Страница 28: ...Introduction xxviii lan SC520 Microcontroller User s Manual...
Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...