The LPC47S45x does not assume any particular timeout. When the host is driving SYNC, it may have to insert a
very large number of wait states, depending on PCI latencies and retries.
SYNC Patterns and Maximum Number of SYNCS
If the SYNC pattern is 0101, then the host assumes that the maximum number of SYNCs is 8.
If the SYNC pattern is 0110, then no maximum number of SYNCs is assumed. The LPC47S45x has protection
mechanisms to complete the cycle. This is used for EPP data transfers and utilizes the same timeout protection that
is in EPP.
SYNC Error Indication
The LPC47S45x reports errors via the LAD[3:0] = 1010 SYNC encoding.
If the host was reading data from the LPC47S45x, data will still be transferred in the next two nibbles. This data may
be invalid, but it will be transferred by the LPC47S45x. If the host was writing data to the LPC47S45x, the data had
already been transferred.
In the case of multiple byte cycles, such as DMA cycles, an error SYNC terminates the cycle. Therefore, if the host is
transferring 4 bytes from a device, if the device returns the error SYNC in the first byte, the other three bytes will not
be transferred.
I/O and DMA START Fields
I/O and DMA cycles use a START field of 0000.
Reset Policy
The following rules govern the reset policy:
When PCI_RESET# goes inactive (high), the clock is assumed to have been running for 100usec prior to the
removal of the reset signal, so that everything is stable. This is the same reset active time after clock is stable
that is used for the PCI bus.
When PCI_RESET# goes active (low):
the host drives the LFRAME# signal high, tristates the LAD[3:0] signals, and ignores the LDRQ# signal.
the LPC47S45x ignores LFRAME#, tristate the LAD[3:0] pins and drive the LDRQ# signal inactive (high).
6.3.3 LPC TRANSFERS
Wait State Requirements
I/O Transfers
The LPC47S45x inserts three wait states for an I/O read and two wait states for an I/O write cycle. A SYNC of 0110
is used for all I/O transfers. The exception to this is for transfers where IOCHRDY would normally be deasserted in
an ISA transfer (i.e., EPP) in which case the sync pattern of 0110 is used and a large number of syncs may be
inserted (up to 330 which corresponds to a timeout of 10us).
DMA Transfers
The LPC47S45x inserts three wait states for a DMA read and four wait states for a DMA write cycle. A SYNC of
0101 is used for all DMA transfers.
See the example timing for the LPC cycles in the “Timing Diagrams” section.
SMSC DS – LPC47S45x
Page 27 of 259
Rev. 07/09/2001
DATASHEET
SMSC [ SMSC CORPORATION ]
