ST STM32F101xx User Manual

RM0008 Flexible static memory controller (FSMC)
Doc ID 13902 Rev 12 525/1096
SRAM/NOR-Flash write timing registers 1..4 (FSMC_BWTR1..4)
Address offset: 0xA000 0000 + 0x104 + 8 * (x – 1), x = 1...4
Reset value: 0x0FFF FFFF
This register contains the control information of each memory bank, used for SRAMs, ROMs
and NOR Flash memories. When the EXTMOD bit is set in the FSMC_BCRx register, then
this register is active for write access.
313029282726252423222120191817161514131211109876543210
Res.
ACCM
OD
DATLAT CLKDIV
Reserved
DATAST ADDHLD ADDSET
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bits 29:28 ACCMOD: Access mode.
Specifies the asynchronous access modes as shown in the next timing diagrams.These bits are
taken into account only when the EXTMOD bit in the FSMC_BCRx register is 1.
00: access mode A
01: access mode B
10: access mode C
11: access mode D
Bits 27:24 DATLAT: Data latency (for synchronous burst NOR Flash).
For NOR Flash with Synchronous burst mode enabled, defines the number of memory clock cycles
(+2) to issue to the memory before getting the first data:
0000: (0x0) Data latency of 2 CLK clock cycles for first burst access
...
1111: (0xF) Data latency of 17 CLK clock cycles for first burst access (default value after reset)
Note: This timing parameter is not expressed in HCLK periods, but in Flash clock (CLK) periods
Note: In asynchronous NOR Flash, SRAM or ROM accesses, this value is don’t care.
Note: In case of CRAM, this field must be set to 0
Bits 23:20 CLKDIV: Clock divide ratio (for CLK signal).
Defines the period of CLK clock output signal, expressed in number of HCLK cycles:
0000: Reserved
0001 CLK period = 2 × HCLK periods
0010 CLK period = 3 × HCLK periods
1111: CLK period = 16 × HCLK periods (default value after reset)
In asynchronous NOR Flash, SRAM or ROM accesses, this value is don’t care.
Bits 19:16 Reserved
Bits 15:8 DATAST: Data-phase duration.
These bits are written by software to define the duration of the data phase (refer to Figure 187 to
Figure 198), used in SRAMs, ROMs and asynchronous multiplexed NOR Flash accesses:
0000 0000: Reserved
0000 0001: DATAST phase duration = 2 × HCLK clock cycles
0000 0010: DATAST phase duration = 3 × HCLK clock cycles
...
1111 1111: DATAST phase duration = 16 × HCLK clock cycles (default value after reset)

ST STM32F101xx Specifications

General

Brand	ST
Model	STM32F101xx
Category	Microcontrollers
Language	English