User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 8: PCI Bus and HyperTransport Fabric Page
199
In addition to generating EOI this space can be used to generate HyperTransport interrupt messages. If bits
[4:2] of the address are not equal to 3'b111 (i.e. the message is encoding something other than an EOI) rather
than sending a Posted Broadcast message the bridge will send a Posted Sized Byte Write with a count of zero,
the COMPAT bit clear and a doubleword of zeros as byte masks (the extended destination bits from rev 1.01
and later of the HyperTransport standard are not supported). This is the format of an interrupt message. The
address bits 23:16 indicate the vector, bits 15:8 the destination, bit 7 is Reserved and should be zero, bit 6
indicates the destination mode, bit 5 should be zero to indicate an edge interrupt (level cannot be used because
the interface will not accept the inbound EOI), and bits 4:2 are the interrupt type.
L
EGACY
I
NTERRUPT
A
CKNOWLEDGE
(IACK) S
PACE
Legacy interrupts from a PIC style interrupt controller in the southbridge require an interrupt acknowledgement
(IACK) cycle, this is a byte read that will return the interrupt source vector number. As with the subtractive
decode I/O space, the part supports the southbridge being on either the HyperTransport bus or the PCI as set
by the southOnLDT configuration bit.
If the southbridge is on the PCI then it will signal the interrupt using its INTR pin, which should be routed to one
of the general interrupt inputs. If the southbridge is on the HyperTransport then it signals the interrupt using an
Ext. Int. message, which is translated into interrupt 54 being raised in the CPU interrupt mappers (see
Section: “HyperTransport Interrupts” on page 48
). In either case the interrupt must be acknowledged with an
IACK cycle. This is a byte read that returns the interrupt vector information. The address map defines the
region F (in
) for the CPU to read from to perform an IACK access; the address is
ignored and any access in this range has the same effect. If the southOnLDT bit is set this gets run as a cycle
on the HyperTransport to the special address range (
FD_F900_0000
-
FD_F90F_FFFF
) with the COMPAT bit
set. If the southOnLDT bit is clear, the read gets run as an IACK cycle on the PCI bus.
PCI F
ULL
A
CCESS
S
PACE
Regions O and P in
are provided to allow the CPU to generate any memory space
address on the PCI bus. When the interface is configured in Device Mode the address map used on the PCI
bus matches the host system and not the internal address map. The full access space allows the device to
access any host system address, as would be expected for a PCI peripheral. The bottom 32 bits of the address
are used directly to form the PCI bus address. Address bit [32] is used to select between the two regions and
therefore the endian policy used for accesses. The full access space is available when the interface is in Host
Mode, but it is less useful. The PCI interface will not respond to requests that it generates, any access through
Full Access space to an address with a destination in the part will result in a master abort.
There is no equivalent I/O full access space, since the normal I/O space can be used in Device Mode to
generate 25 bit I/O addresses on the PCI bus.
S
PECIAL
H
YPER
T
RANSPORT
S
PACE
The HyperTransport defines a range of address space for other special cycles. None are directly supported by
the interface, however access is provided to the special range using region G in
. Use
of addresses in this region requires understanding of the HyperTransport specification. Since no assistance is
provided for the special use, accesses in this region may not be useful, and can result in UNDEFINED
behavior. Address bit [29] is used to select between the endian policies.
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