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:
1) When nPCI_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.
2) When nPCI_RESET goes active (low):
a) the host drives the nLFRAME signal high, tristates the LAD[3:0] signals, and ignores the nLDRQ signal.
b) the LPC47B27x must ignore nLFRAME, tristate the LAD[3:0] pins and drive the nLDRQ signal inactive
(high).
LPC TRANSFERS
Wait State Requirements
I/O Transfers
The LPC47B27x 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 or IrCC transfers) 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 LPC47B27x 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 LPC47B27x
- 22 -
Rev. 08-10-04
DATASHEET
SMSC [ SMSC CORPORATION ]
