125
Peripheral Local Bus
8.1.4
Flash Memory Support
PBI peripheral bus interface supports 8-, or 16- bit Flash devices.
The PBI provides programmable wait state functionality for peripheral memory windows.
Note:
Potentially, programmable wait state functionality could be connected to any peripheral device that
has a deterministic wait state profile. However, data valid and turn-around times need to fit within
parameters provided by programmable wait state profiles to support Flash devices.
Any write transactions issued to a Flash address space window must always represent a single flash
bus data cycle (
strb, strh
).
The peripheral chip enables,
PCE[1:0]#
, activate the appropriate Peripheral window when the
address falls within one of the Peripheral address ranges.
Note:
By default, bank 0 is enabled with the maximum number of Address-to-Data and Recovery Wait
states. The width of the interface can be strapped for either 8-bit wide Flash or 16-bit wide flash.
Thus,
PCE0#
is the Peripheral Bus chip enable to be used for booting purposes.
shows how two 8-bit Flash devices interface with 80331through the PBI Interface.
z
Refer to
for the programmable address-to data and recovery wait states. These numbers
are based on a 66 MHz internal clock for the PBI interface.
Figure 63.
Four MByte Flash Memory System
1
1.
16-bit wide flash devices requires two latches.
Latch
A[2:0 ]
ALE
AD[22:16]
POE#
PWE#
PCE0#
PCE1#
I/O
Processor
A[20:0]
OE#
WE#
DQ[7:0]
CE#
Intel 28F016-70
16 Mbit Flash
A[20:0]
OE#
WE#
DQ[7:0]
CE#
Intel 28F016-70
16 Mbit Flash
A[2:0]
A[2:0]
A[20:16]
A[7:3]
DQ[7:0]
A[20:16]
AD[7:3]
AD[15:0]
A[15:8]
AD[15:8]
Table 72.
Flash Wait State Profile Programming
1
1.
Each Wait State Represents 15 ns.
Flash Speed
Address-to-Data Wait States
Recovery Wait States
<= 55 ns
4
0
<= 115 ns
8
2
<= 150 ns
10
2
Summary of Contents for 80331
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