PCI Bus Host Bridge
Élan™SC520 Microcontroller User’s Manual
9-9
■
The LOCK pin is an optional pin not required in most systems, because other
mechanisms are typically employed for coherency.
■
Address/data stepping is not supported as a master due to the performance implications.
■
The ÉlanSC520 microcontroller does not support a downstream “Southbridge” device,
because most peripherals normally included in a Southbridge are integrated into the
ÉlanSC520 microcontroller.
■
The optional message-signalled interrupt feature described in the
PCI Local Bus
Specification, Revision 2.2, is not supported in the ÉlanSC520 microcontroller.
9.5.1.1
Unsupported PCI Bus Configuration Registers
Some standard PCI bus configuration registers are not implemented, because the
ÉlanSC520 microcontroller is a host-to-PCI bridge and does not support some optional PCI
functionality.
■
Base Address registers are not implemented, because the ÉlanSC520 microcontroller
is the host PCI device. Target address space configuration is done through ÉlanSC520
microcontroller-specific configuration (see “PCI Host Bridge Target Address Space” on
page 9-18).
■
Latency timer and MAX_LAT, MIN_GNT are not implemented, because the ÉlanSC520
microcontroller’s PCI host bridge does not support multiple data phase transactions as
a master.
■
Cache line size is not implemented, because the ÉlanSC520 microcontroller PCI host
bridge does not support cacheable PCI memory.
9.5.2
Configuration Information
The PCI host bridge can generate configuration cycles on the PCI bus.
The Configuration Mechanism #1, as defined in the
PCI Local Bus Specification, Revision
2.1, is used. The PCI Configuration Address (PCICFGADR) register resides at I/O address
0CF8h, and the PCI Configuration Data (PCICFGDATA) register resides at I/O address
0CFCh. The Am5
x
86 CPU accesses these two I/O ports to generate PCI configuration
cycles.
The PCI host bridge pre-drives the AD31–AD0 pins for five clocks before asserting FRAME
when performing configuration cycles. This allows IDSEL to settle before the transaction
starts (IDSEL signals may have a slow rise time).
External PCI bus devices require an IDSEL pin to allow configuration from the ÉlanSC520
microcontroller’s PCI bus host bridge. The method implemented for IDSEL generation is
system-specific; however, the ÉlanSC520 microcontroller implements the commonly used
practice in which the AD31–AD11 pins are asserted for IDSEL generation during the
configuration cycles (the host bridge uses AD11). In this scheme, the AD12 is IDSEL for
device number 1, AD13 is IDSEL for device number 2, etc. The AD pins are asserted during
configuration cycles according to the decode of the PCI bus device; thus, this scheme is
limited to 20 devices on the PCI bus.
The ÉlanSC520 microcontroller’s PCI bus host bridge is hardwired to device number 0
(AD11), and the host bridge PCI bus configuration registers are accessed through the PCI
Configuration Address (PCICFGADR) register (Port 0CF8h) and PCI Configuration Data
(PCICFGDATA) register (Port 0CFCh), like any external PCI device. An external PCI bus
configuration cycle is not generated when the Am5
x
86 CPU configures the internal PCI
host bridge registers.
Содержание Elan SC520
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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...