Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
557
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
In page mode, the programming of the read timings is described in
:
The SMC does not check the coherency of timings. It will always apply the NCS_RD_PULSE timings as page
access timing (t
access timing (t
pa
) and the NRD_PULSE for accesses to the page (t
sa
), even if the programmed value for t
pa
is
shorter than the programmed value for t
sa
.
28.14.2 Page Mode Restriction
The page mode is not compatible with the use of the NWAIT signal. Using the page mode and the NWAIT signal
may lead to unpredictable behavior.
may lead to unpredictable behavior.
28.14.3 Sequential and Non-sequential Accesses
If the chip select and the MSB of addresses as defined in
are identical, then the current access lies in
the same page as the previous one, and no page break occurs.
Using this information, all data within the same page, sequential or not sequential, are accessed with a minimum
access time (t
access time (t
sa
).
illustrates access to an 8-bit memory device in page mode, with 8-byte pages.
Access to D1 causes a page access with a long access time (t
pa
). Accesses to D3 and D7, though they are not
sequential accesses, only require a short access time (t
sa
).
If the MSB of addresses are different, the SMC performs the access of a new page. In the same way, if the chip
select is different from the previous access, a page break occurs. If two sequential accesses are made to the page
mode memory, but separated by another internal or external peripheral access, a page break occurs on the
second access because the chip select of the device was deasserted between both accesses.
select is different from the previous access, a page break occurs. If two sequential accesses are made to the page
mode memory, but separated by another internal or external peripheral access, a page break occurs on the
second access because the chip select of the device was deasserted between both accesses.
Table 28-6.
Programming of Read Timings in Page Mode
Parameter
Value
Definition
READ_MODE
‘x’ No
impact
NCS_RD_SETUP
‘x’ No
impact
NCS_RD_PULSE
t
pa
Access time of first access to the page
NRD_SETUP
‘x’
No impact
NRD_PULSE
t
sa
Access time of subsequent accesses in the page
NRD_CYCLE
‘x’
No impact