ST STM32F100 Series Reference Manual page 530

Flexible static memory controller (FSMC)
Bits 19:16 BUSTURN[3:0]: Bus turnaround phase duration
These bits are written by software to add a delay at the end of a write-to-read (and read-to
write) transaction. The programmed bus turnaround delay is inserted between an
asynchronous read (muxed or D mode) or a write transaction and any other
asynchronous/synchronous read or write to/from a static bank (for a read operation, the bank
can be the same or a different one; for a write operation, the bank can be different except in r
muxed or D mode).
In some cases, the bus turnaround delay is fixed, whatever the programmed BUSTURN
values:
– No bus turnaround delay is inserted between two consecutive asynchronous write transfers
to the same static memory bank except in muxed and D mode.
– A bus turnaround delay of 1 FSMC clock cycle is inserted between:
– A bus turnaround delay of 2 FSMC clock cycles is inserted between:
– A bus turnaround delay of 3 FSMC clock cycles is inserted between:
0000: BUSTURN phase duration = 0 HCLK clock cycle added
...
1111: BUSTURN phase duration = 15 × HCLK clock cycles (default value after reset)
530/709
– Two consecutive asynchronous read transfers to the same static memory bank
except for muxed and D modes.
– An asynchronous read to an asynchronous or synchronous write to any static bank
or dynamic bank except for muxed and D modes.
– An asynchronous (modes 1, 2, A, B or C) read and a read operation from another
static bank.
– Two consecutive synchronous write accesses (in burst or single mode) to the same
bank
– A synchronous write (burst or single) access and an asynchronous write or read
transfer to or from static memory bank (the bank can be the same or different in case
of a read operation).
– Two consecutive synchronous read accesses (in burst or single mode) followed by a
any synchronous/asynchronous read or write from/to another static memory bank.
– Two consecutive synchronous write operations (in burst or single mode) to different
static banks.
– A synchronous write access (in burst or single mode) and a synchronous read
access from the same or to a different bank.
RM0041 Rev 6
RM0041