at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 229

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

21.13.2
21.13.3
21.13.4
6249D–ATARM–20-Dec-07
Byte Access Type in Page Mode
Page Mode Restriction
Sequential and Non-sequential Accesses
timings are identical. The pulse length of the first access to the page is defined with the
NCS_RD_PULSE field of the SMC_PULSE register. The pulse length of subsequent accesses
within the page are defined using the NRD_PULSE parameter.
In page mode, the programming of the read timings is described in
Table 21-8.
The SMC does not check the coherency of timings. It will always apply the NCS_RD_PULSE
timings as page access timing (t
the programmed value for t
The Byte Access Type configuration remains active in page mode. For 16-bit or 32-bit page
mode devices that require byte selection signals, configure the BAT field of the
SMC_REGISTER to 0 (byte select access type).
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.
If the chip select and the MSB of addresses as defined in
rent 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
page mode, with 8-byte pages. Access to D1 causes a page access with a long access time
(t
access time (t
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 sequen-
tial accesses are made to the page mode memory, but separated by an other 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.
Parameter
READ_MODE
NCS_RD_SETUP
NCS_RD_PULSE
NRD_SETUP
NRD_PULSE
NRD_CYCLE
pa
). Accesses to D3 and D7, though they are not sequential accesses, only require a short
sa
Programming of Read Timings in Page Mode
).
Value
‘x’
‘x’
t
‘x’
t
‘x’
pa
sa
pa
is shorter than the programmed value for t
sa
pa
).
) and the NRD_PULSE for accesses to the page (t
Figure 21-35
Definition
No impact
No impact
Access time of first access to the page
No impact
Access time of subsequent accesses in the page
No impact
AT91SAM9263 Preliminary
illustrates access to an 8-bit memory device in
Table 21-7
Table
are identical, then the cur-
sa
.
21-8:
sa
), even if
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