RM0090: Reference manual - STMicroelectronics

RM0090 Flexible static memory controller (FSMC)
During wait-state insertion via the NWAIT signal, the controller continues to send clock
pulses to the memory, keeping the chip select and output enable signals valid, and does not
consider the data valid.
There are two timing configurations for the NOR Flash NWAIT signal in burst mode:
● Flash memory asserts the NWAIT signal one data cycle before the wait state (default
after reset)
● Flash memory asserts the NWAIT signal during the wait state
These two NOR Flash wait state configurations are supported by the FSMC, individually for
each chip select, thanks to the WAITCFG bit in the FSMC_BCRx registers (x = 0..3).
Figure 419. Wait configurations
HCLK
CLK
A[25:16]
NADV
NWAIT
(WAITCFG = 0)
NWAIT
(WAITCFG = 1)
A/D[15:0]
addr[25:16]
Memory transaction = burst of 4 half words
Addr[15:0] data data
inserted wait state
data
ai15798
Doc ID 018909 Rev 3 1340/1416