Figure 54. Burst Write Sdram Access Waveforms - ST STM32F446 Series Reference Manual

Flexible memory controller (FMC)
Note: If two SDRAM devices are connected to the FMC, all the accesses performed at the same
time to both devices by the Command Mode register (Load Mode Register command) are
issued using the timing parameters configured for SDRAM Bank 1 (TMRD andTRAS
timings) in the FMC_SDTR1 register.
SDRAM controller write cycle
The SDRAM controller accepts single and burst write requests and translates them into
single memory accesses. In both cases, the SDRAM controller keeps track of the active row
for each bank to be able to perform consecutive write accesses to different banks (Multibank
ping-pong access).
Before performing any write access, the SDRAM bank write protection must be disabled by
clearing the WP bit in the FMC_SDCRx register.
The SDRAM controller always checks the next access.
• If the next access is in the same row or in another active row, the write operation is
carried out,
•
if the next access targets another row (not active), the SDRAM controller generates a
precharge command, activates the new row and initiates a write command.
SDRAM controller read cycle
The SDRAM controller accepts single and burst read requests and translates them into
single memory accesses. In both cases, the SDRAM controller keeps track of the active row
in each bank to be able to perform consecutive read accesses in different banks (Multibank
ping-pong access).
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Figure 54. Burst write SDRAM access waveforms

RM0390 Rev 4
RM0390