Flexible memory controller (FMC) RM0390
292/1328 RM0390 Rev 4
Note: PSRAMs (CRAMs) have a variable latency due to internal refresh. Therefore these
memories issue the NWAIT signal during the whole latency phase to prolong the latency as
needed.
With PSRAMs (CRAMs) the filled DATLAT must be set to 0, so that the FMC exits its latency
phase soon and starts sampling NWAIT from memory, then starts to read or write when the
memory is ready.
This method can be used also with the latest generation of synchronous Flash memories
that issue the NWAIT signal, unlike older Flash memories (check the datasheet of the
specific Flash memory being used).
SRAM/NOR-Flash write timing registers 1..4 (FMC_BWTR1..4)
Address offset: 0x104 + 8 * (x – 1), x = 1...4
Reset value: 0x0FFF FFFF
This register contains the control information of each memory bank. It is used for SRAMs,
PSRAMs and NOR Flash memories. When the EXTMOD bit is set in the FMC_BCRx
register, then this register is active for write access.
Bits 7:4 ADDHLD[3:0]: Address-hold phase duration
These bits are written by software to define the duration of the address hold phase (refer to
Figure 34 to Figure 46), used in mode D or multiplexed accesses:
0000: Reserved
0001: ADDHLD phase duration =1 × HCLK clock cycle
0010: ADDHLD phase duration = 2 × HCLK clock cycle
...
1111: ADDHLD phase duration = 15 × HCLK clock cycles (default value after reset)
For each access mode address-hold phase duration, refer to the respective figure (Figure 34
to Figure 46).
Note: In synchronous accesses, this value is not used, the address hold phase is always 1
memory clock period duration.
Bits 3:0 ADDSET[3:0]: Address setup phase duration
These bits are written by software to define the duration of the address setup phase (refer to
Figure 34 to Figure 46), used in SRAMs, ROMs, asynchronous NOR Flash and PSRAM:
0000: ADDSET phase duration = 0 × HCLK clock cycle
...
1111: ADDSET phase duration = 15 × HCLK clock cycles (default value after reset)
For each access mode address setup phase duration, refer to the respective figure
(Figure 34 to Figure 46).
Note: In synchronous accesses, this value is don’t care.
In Muxed mode or Mode D, the minimum value for ADDSET is 1.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res. Res. ACCMOD Res. Res. Res. Res. Res. Res. Res. Res. BUSTURN
rw rw rw rw rw rw
1514131211109876543210
DATAST ADDHLD ADDSET[3:0]
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bits 31:30 Reserved, must be kept at reset value
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