Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—PCI Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Develepor’s Manual
August 2006
526
Order Number: 306262-004US
10.3.2.2.2
Initiator Read Transactions
The PCI Master Interface receives read requests from the AHB Slave Interface or PCI-
to-AHB DMA Controller via the Initiator Request FIFO. Read data is supplied to the AHB
side using the Initiator Receive FIFO. The Master Interface transfers the indicated
number of words from the PCI bus to the FIFO. The following rules apply to the read
transfers:
• For memory read operations, if the cache line size indicated in the PCI
Configuration Register pci_bhlc is zero, the Memory Read command is used on PCI.
For non-zero cache-line sizes, the starting address and word count of the transfer
are used to determine how many cache lines will be read. If one full cache line is to
be read, the Memory Read Line command is used. If two or more full cache lines,
the Memory Read Multiple command is used. Note that read commands may
change from transaction to transaction during long burst reads that are broken up
by retries or disconnects.
• If the Receive FIFO becomes full, the Master Interface terminates the cycle on the
PCI bus using a disconnect. When room becomes available, the transfer resumes
using the address of the next word to be read.
• If the master’s Latency Timer expires, the Master Interface terminates the cycle on
the PCI bus. The transfer resumes at the first opportunity using address of the next
word to be read.
• If a retry or target disconnect is received before the transfer ends, the Master
Interface resumes the transfer at the first opportunity using the address of the next
data word to be read.
• If a master abort occurs, the AHB side transaction is terminated with an ERROR
response and the Received Master Abort bit is set in the PCI Configuration status
register.
• If a target abort is received, the AHB side transaction is terminated with an ERROR
response and the Received Target Abort bit is set in the PCI Configuration status
register.
10.3.2.2.3
Master Latency Timer
When the Initiator Interface begins PCI transaction it begins to decrement its master
latency timer. When the timer value reaches zero, the PCI grant input is checked. If the
grant is deasserted, the Initiator Interface deasserts PCI_FRAME_N (if it is still
asserted) at the earliest opportunity (normally the next data phase for all
transactions). The transfer is resumed as soon as possible at the address of the next
word.
10.3.2.2.4
Initiator Special Cycles
Special Cycles are broadcast to all PCI targets on the bus and are terminated by Master
Abort. No error is signaled in this case.
10.3.2.3
PCI Host Functions
A logic high state on the exp_pcihost input port indicates that the PCI Controller should
function in host mode. In this mode, access to the PCI Configuration registers is only
allowed from the AHB via the CSR-based configuration access port. In non-host mode
(exp_pcihost = 0), access is only allowed from the external PCI bus.
The following sections describe PCI host functions that do not directly affect PCI
Controller functionality.