6-48 Intel® PXA26x Processor Family Developer’s Manual
Memory Controller
6.8.3 ROM Interface

The processor provides programmable timing for both bu rst and non-burst ROMs. The RDF field

in MSCx is the latency (in memory clock cycles) for the first, and all subsequent, data beats from

non-burst ROMs, and the first data beat from a burst ROM. RDN is the latency for the burst data

beats after the first for burst ROMs. RRR delays the following access to a different memory space

to allow time for the current ROM to three-state the data bus.

RRR must be programmed with the maximum tOFF value, as specified by the ROM manufacturer.

For hardware reset initialization values, refer to Section6.9, “16-Bit PC C ard/Compact Flash

Interface” on page 6-57. MSC0[15:0] is selected when the address space corresponding to nCS0 is

accessed. The processor supports a ROM burst size of 1, 4, or 8 by configuring the MSCx[RTx]

register bits to 0, 2 or 3 respectfully.

6.8.3.1 ROM Timing Diagrams and Parameters

The timings for burst and non-burst ROMs are shown in Figure6-14, Figure 6-15, and Figure6-16.

010 Burst-of-4
ROM or Flash
(non- burst writes)
RDF+1
(0,4)
RDN+1
(1:3,5:7)
RDF+1
(0,4)
RDN+1
(1:3,5:7)
0 N/A RDF+1 N/A
011
Burst-of-8
ROM or Flash
(non-burst writes)
RDF+1
(0)
RDN+1
(1:7)
RDF+1
(0)
RDN+1
(1:7)
0 N/A RDF+1 N/A
100 Variabl e
Latency I/O
RDF+
RDN+2+waits
RDF+1+
waits RDN+1 RDF+
RDN+2+waits
RDF+1+
waits RDN+1

Table 6-26. Asynchronous Static Memory and Variable Latency I/O Capabilities (Sheet 2 of 2)

MSCx[RTx] Device
Type
Timing (Memory Clocks)
Burst
Read
Address
Assert
nOE
Assert
Burst
nOE
Deassert
Burst
Write
Address
Assert
nWE
Assert
Burst
nWE
Deassert