at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 204

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

22.5
22.5.1
Figure 22-2. Write Burst, 32-bit SDRAM Access
SDRAMC_A[12:0]
22.5.2
204
D[31:0]
SDWE
SDCS
SDCK
Functional Description
RAS
CAS
AT91SAM9G20 Preliminary
SDRAM Controller Write Cycle
SDRAM Controller Read Cycle
Row n
The SDRAM Controller allows burst access or single access. In both cases, the SDRAM control-
ler keeps track of the active row in each bank, thus maximizing performance. To initiate a burst
access, the SDRAM Controller uses the transfer type signal provided by the master requesting
the access. If the next access is a sequential write access, writing to the SDRAM device is car-
ried out. If the next access is a write-sequential access, but the current access is to a boundary
page, or if the next access is in another row, then the SDRAM Controller generates a precharge
command, activates the new row and initiates a write command. To comply with SDRAM timing
parameters, additional clock cycles are inserted between precharge/active (t
active/write (t
Configuration Register” on page
The SDRAM Controller allows burst access, incremental burst of unspecified length or single
access. In all cases, the SDRAM Controller keeps track of the active row in each bank, thus
maximizing performance of the SDRAM. If row and bank addresses do not match the previous
row/bank address, then the SDRAM controller automatically generates a precharge command,
activates the new row and starts the read command. To comply with the SDRAM timing param-
eters, additional clock cycles on SDCK are inserted between precharge and active commands
(t
uration register of the SDRAM Controller. After a read command, additional wait states are
generated to comply with the CAS latency (1, 2 or 3 clock delays specified in the configuration
register).
RP
) and between active and read command (t
t
RCD
= 3
col a
RCD
Dna
) commands. For definition of these timing parameters, refer to the
col b
Dnb
col c
Dnc
214. This is described in
col d
Dnd
col e
Dne
RCD
col f
Dnf
). These two parameters are set in the config-
col g
Dng
Figure 22-2
col h
Dnh
col i
Dni
below.
col j
Dnj
6384B–ATARM–15-Dec-08
RP
) commands and
col k
Dnk
“SDRAMC
col l
Dnl