49.7.2 QSPI Mode Register


Bit	31	30	29	28	27	26	25	24
	DLYCS[7:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	23	22	21	20	19	18	17	16
	DLYBCT[7:0]
Access	R/W	R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset	0	0	0	0	0	0	0	0


Bit	15	14	13	12	11	10	9	8
					NBBITS[3:0]
Access					R/W	R/W	R/W	R/W
Reset					0	0	0	0


Bit	7	6	5	4	3	2	1	0
			CSMODE[1:0]		SMRM	WDRBT	LLB	SMM
Access			R/W	R/W	R/W	R/W	R/W	R/W
Reset			0	0	0	0	0	0

Bits 31:24 – DLYCS[7:0] Minimum Inactive QCS Delay

This field defines the minimum delay between the deactivation and the activation of QCS. The DLYCS time guarantees the client minimum deselect time.

If DLYCS written to ‘0’, one peripheral clock period is inserted by default.

Otherwise, the following equation determines the delay:

DLYCS = Minimum inactive × f_{peripheral clock}

Bits 23:16 – DLYBCT[7:0] Delay Between Consecutive Transfers

This field defines the delay between two consecutive transfers with the same peripheral without removing the chip select. The delay is always inserted after each transfer and before removing the chip select if needed.

When DLYBCT is written to ‘0’, no delay between consecutive transfers is inserted and the clock keeps its duty cycle over the character transfers. In Serial Memory mode (SMM = 1), DLYBCT must be written to ‘0’ and no delay is inserted.

Otherwise, the following equation determines the delay:

DLYBCT = (Delay Between Consecutive Transfers × f_{peripheral clock}) / 32

Bits 11:8 – NBBITS[3:0] Number Of Bits Per Transfer

NBBITS is used only when SMM is set to '0'.

Value	Name	Description
0	8_BIT	8 bits for transfer
8	16_BIT	16 bits for transfer

Bits 5:4 – CSMODE[1:0] Chip Select Mode

The CSMODE field determines how the chip select is deasserted

Note: This field is forced to LASTXFER when SMM is written to ‘1’.

Value	Name	Description
0	NOT_RELOADED	The chip select is deasserted if QSPI_TDR.TD has not been reloaded before the end of the current transfer.
1	LASTXFER	The chip select is deasserted when the bit LASTXFER is written to ‘1’ and the character written in QSPI_TDR.TD has been transferred.
2	SYSTEMATICALLY	The chip select is deasserted systematically after each transfer.

Bit 3 – SMRM Serial Memory Register Mode

Value	Description
0	Serial Memory registers are written via system bus access. See section Instruction Frame Transmission for details.
1	Serial Memory registers are written via peripheral bus (configuration bus) access. See section Instruction Frame Transmission for details.

Bit 2 – WDRBT Wait Data Read Before Transfer

0 (DISABLED): No effect. In SPI mode, a transfer can be initiated whatever the state of the QSPI_RDR is.

1 (ENABLED): In SPI mode, a transfer can start only if the QSPI_RDR is empty, i.e., does not contain any unread data. This mode prevents overrun error in reception.