System Address Mapping
Élan™SC520 Microcontroller User’s Manual
4-13
■
If necessary, PARx registers can be used to override sending accesses to the PCI bus
on an individual peripheral basis. In this way, accesses for individual peripherals can be
directed back to the external GP bus.
For example, some PCI cards (notably VGA cards) use legacy I/O locations. The
IO_HOLE_DEST bit allows the holes to be directed to either the PCI or to the GP bus. For
a system requiring legacy GP bus peripherals along with legacy PCI peripherals (for
instance, a PCI VGA card and a GP bus keyboard controller), the IO_HOLE_DEST bit
would be set to 1 to direct all accesses to the PCI bus. The legacy GP bus keyboard
controller would then be configured via PAR registers to override this setting. See “VGA
Controller on the PCI Bus” on page 3-15 for another discussion of this topic.
Note: If a PARx register is configured to address GP bus I/O space within a hole, accesses
in the defined region are forwarded to the GP bus regardless of the IO_HOLE_DEST bit
value. It is the programmer’s responsibility to ensure that external peripherals are not
mapped over any of the ÉlanSC520 microcontroller’s internal peripherals. Normal operation
is not guaranteed in this case. See “Disabling Internal Peripherals” on page 3-21 for more
information about this topic.
Table 4-5
PC/AT Peripherals I/O Map
Peripheral Core
I/O Address Range
Slave GP-DMA Controller
0000–000Fh
Master Interrupt Controller
0020–0021h
Slave 2 Interrupt Controller
•
This controller is not defined in standard PC/AT architecture, but has been included
in the ÉlanSC520 microcontroller to provide additional interrupt request sources
0024–0025h
Programmable Interval Timer (PIT)
0040–0043h
Keyboard Control A20M and Fast Reset (SCP)
•
Accesses to these locations are always directed to the external GP bus, but are
also snooped internally for PC/AT functions.
0060h, 0064h
System Control Port B/NMI Status
•
Reads and writes to this location are directed to this register only and are not seen
on the external GP bus
0061h
Real-Time Clock (RTC) Index/Data
0070h, 0071h
General-Purpose Scratch Registers
•
These are unused locations from the original DMA Page Register file and are
maintained for PC/AT compatibility. Writes to these locations update the
corresponding register and are also seen on the external GP bus. Reads to the
locations return the data from the corresponding register, but do not initiate a cycle
on the external GP bus.
0080h
0084–0086h
0088h
008C–008Eh
General-Purpose Scratch Register
•
This is an unused location from the original DMA Page Register file and is
maintained for PC/AT compatibility. Reads and writes to this location are directed
to this register only and are not seen on the external GP bus.
008Fh
GP-DMA Page Registers
•
Reads and writes to these locations are directed to these registers only and are not
seen on the external GP bus.
0081–0083h
0087h
0089h-008Bh
System Control Port A
0092h
Slave 1 Interrupt Controller
00A0–00A1h
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...