XMEGAA Datasheet, PDF (249/375 Pages) ATMEL Corporation – 8-bit XMEGAA Microcontroller

ATXMEGA
22.8.1
Supported Commands
The SDRAM commands that are supported by the EBI is listed in Table 22-3 on page 249.
Table 22-3. Supported SDRAM commands
Command
Description
NOP
No Operation
ACTIVE
Activate the selected bank and select the row.
READ
Input the starting column address and begin the burst read operation.
WRITE
Input the starting column address and begin the burst write operation.
PRECHARGE
Deactivate the open row of selected bank or all banks
AUTO REFRESH Refresh one row of each bank
LOAD MODE
SELF REFRESH Activate self refresh mode
22.8.2
3-Port EBI Configuration
When 3 EBI ports are available, SDRAM can be connected with 3-Port EBI configuration. When
this is done only 4-bit data bus is available, and any chip select must be controlled from software
using a general purpose I/O pin (Pxn).
Figure 22-8. 3-Port SDRAM configuration
EBI
CLK
CKE
BA[1:0]
DQM
WE
RAS
CAS/RE
CLK
CKE
BA[1:0]
DQM
WE
RAS
CAS _SDRAM
D[3:0]
A[7:0]]
A[11:8]
D[3:0]
A[7:0]
A[11:8]
Pxn
CS
22.8.3
4-Port EBI Configuration
When 4 EBI ports are available, SDRAM can be connected with 3-Port or 4-Port EBI configura-
tion. When 4-Port configuration is used, 8-bit data bus is available and all four chip selects will
be available.
8077B–AVR–06/08
249