ST STM32F446 Series User Manual

Flexible memory controller (FMC) RM0390
318/1328 RM0390 Rev 4
Bits 23:20 TRP[3:0]: Row precharge delay
These bits define the delay between a Precharge command and another command in number of
memory clock cycles. The TRP timing is only configured in the FMC_SDTR1 register. If two
SDRAM devices are used, the TRP must be programmed with the timing of the slowest device.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: The corresponding bits in the FMC_SDTR2 register are don’t care.
Bits 19:16 TWR[3:0]: Recovery delay
These bits define the delay between a Write and a Precharge command in number of memory clock
cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: TWR must be programmed to match the write recovery time (t
WR
) defined in the SDRAM
datasheet, and to guarantee that:
TWR ≥ TRAS - TRCD and TWR ≥TRC - TRCD - TRP
Example: TRAS= 4 cycles, TRCD= 2 cycles. So, TWR >= 2 cycles. TWR must be
programmed to 0x1.
If two SDRAM devices are used, the FMC_SDTR1 and FMC_SDTR2 must be programmed
with the same TWR timing corresponding to the slowest SDRAM device.
Bits 15:12 TRC[3:0]: Row cycle delay
These bits define the delay between the Refresh command and the Activate command, as well as
the delay between two consecutive Refresh commands. It is expressed in number of memory clock
cycles. The TRC timing is only configured in the FMC_SDTR1 register. If two SDRAM devices are
used, the TRC must be programmed with the timings of the slowest device.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: TRC must match the TRC and TRFC (Auto Refresh period) timings defined in the SDRAM
device datasheet.
Note: The corresponding bits in the FMC_SDTR2 register are don’t care.
Bits 11:8 TRAS[3:0]: Self refresh time
These bits define the minimum Self-refresh period in number of memory clock cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Bits 7:4 TXSR[3:0]: Exit Self-refresh delay
These bits define the delay from releasing the Self-refresh command to issuing the Activate
command in number of memory clock cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: If two SDRAM devices are used, the FMC_SDTR1 and FMC_SDTR2 must be programmed
with the same TXSR timing corresponding to the slowest SDRAM device.

ST STM32F446 Series Specifications

General

Brand	ST
Model	STM32F446 Series
Category	Microcontrollers
Language	English