Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
715
Peripheral Bus Interface Unit—Intel
®
81341 and 81342
9.2.6.1
Flash Read Cycle
Reading a Flash device involves driving the address, output enable, and chip enable.
Depending on the speed of the Flash device, the data returns several cycles later.
The definition of address-to-data wait states are the number of cycles between the
assertion of
PCE[1:0]#
, and the arrival of data from the Flash device on
D[7:0]
(8-bit
Flash). The definition of recovery wait states are the number of cycles between the
data arrival on
D[7:0]
and the address for the next Peripheral transaction.
Address-to-data and recovery wait states are programmed in PBBAR0 and PBBAR1 and
are identical for reads and writes. Since the read wait state requirement is typically
greater, the write wait state requirement is insured to be met.
illustrates a single read cycle example for a 120 ns Flash device. The
number of wait states used for address-to-data is provided by the Address-to-Data
Wait States field in the PBBARx.
Figure 109. 120 ns Flash Single Transfer Read Cycle
A[24:03]
A[02:00]
Ta2
Tw1
Tw8
Td 2
Tr1
Tr4
POE #
PWE #
PCEx #
D[15:00]
D_in
Ti/Ta
Ta1
Td 1
B6269-01