Atmel Evaluation Kit AT91SAM9X25-EK AT91SAM9X25-EK Data Sheet
Product codes
AT91SAM9X25-EK
416
SAM9X25 [DATASHEET]
11054E–ATARM–10-Mar-2014
29.14 Asynchronous Page Mode
The SMC supports asynchronous burst reads in page mode, providing that the page mode is enabled in the SMC_MODE
register (PMEN field). The page size must be configured in the SMC_MODE register (PS field) to 4, 8, 16 or 32 bytes.
register (PMEN field). The page size must be configured in the SMC_MODE register (PS field) to 4, 8, 16 or 32 bytes.
The page defines a set of consecutive bytes into memory. A 4-byte page (resp. 8-, 16-, 32-byte page) is always aligned
to 4-byte boundaries (resp. 8-, 16-, 32-byte boundaries) of memory. The MSB of data address defines the address of the
page in memory, the LSB of address define the address of the data in the page as detailed in
to 4-byte boundaries (resp. 8-, 16-, 32-byte boundaries) of memory. The MSB of data address defines the address of the
page in memory, the LSB of address define the address of the data in the page as detailed in
With page mode memory devices, the first access to one page (t
pa
) takes longer than the subsequent accesses to the
page (t
sa
) as shown in
. When in page mode, the SMC enables the user to define different read timings for
the first access within one page, and next accesses within the page.
Notes: 1. A denotes the address bus of the memory device
2. For 16-bit devices, the bit 0 of address is ignored. For 32-bit devices, bits [1:0] are ignored.
29.14.1 Protocol and Timings in Page Mode
)
The NRD and NCS signals are held low during all read transfers, whatever the programmed values of the setup and hold
timings in the User Interface may be. Moreover, the NRD and NCS 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.
timings in the User Interface may be. Moreover, the NRD and NCS 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.
Table 29-6. Page Address and Data Address within a Page
Page Size
Data Address in the Page
4 bytes
A[25:2]
A[1:0]
8 bytes
A[25:3]
A[2:0]
16 bytes
A[25:4]
A[3:0]
32 bytes
A[25:5]
A[4:0]
A[MSB]
NCS
MCK
NRD
D[31:0]
NCS_RD_PULSE
NRD_PULSE
NRD_PULSE
tsa
tpa
tsa
A[LSB]