Flexible static memory controller (FSMC)
RM0365
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DocID025202 Rev 7
WAIT management in asynchronous accesses
If the asynchronous memory asserts the WAIT signal to indicate that it is not yet ready to
accept or to provide data, the ASYNCWAIT bit has to be set in FMC_BCRx register.
If the WAIT signal is active (high or low depending on the WAITPOL bit), the second access
phase (Data setup phase), programmed by the DATAST bits, is extended until WAIT
becomes inactive. Unlike the data setup phase, the first access phases (Address setup and
Address hold phases), programmed by the ADDSET and ADDHLD bits, are not WAIT
sensitive and so they are not prolonged.
The data setup phase must be programmed so that WAIT can be detected 4 HCLK cycles
before the end of the memory transaction. The following cases must be considered:
1 MUXEN
0x1
0 MBKEN
0x1
Table 68. FMC_BTRx bit fields
Bit No.
Bit name
Value to set
31:30
Reserved
0x0
29-28
ACCMOD
0x0
27-24
DATLAT
Don’t care
23-20
CLKDIV
Don’t care
19-16
BUSTURN
Time between NEx high to NEx low (BUSTURN HCLK)
15-8
DATAST
Duration of the second access phase (DATAST HCLK cycles for
read accesses and 1 HCLK cycles for write accesses).
7-4
ADDHLD
Duration of the middle phase of the access (ADDHLD HCLK cycles).
3-0
ADDSET
Duration of the first access phase (ADDSET HCLK cycles).
Minimum value for ADDSET is 1.
Table 67. FMC_BCRx bit fields (continued)
Bit No.
Bit name
Value to set