46.10.89 TWI Filter Register

Important:

FILT and THRES are used to configure digital filters on data and clock lines.

In Standard, Fast and Fast Plus modes, the digital filter must be enabled (FILT=1) and a pulse width threshold defined (THRES > 0).

The field THRES must be set according to the peripheral clock to suppress spikes lower than 50 ns. The recommended value is calculated using the formula below:

THRES > 50 ns/t_{peripheral_clock (ns)}

Name:	FLEX_TWI_FILTR
Offset:	0x644
Reset:	0x00000000
Property:	Read/Write


Bit	31	30	29	28	27	26	25	24

Access
Reset


Bit	23	22	21	20	19	18	17	16

Access
Reset


Bit	15	14	13	12	11	10	9	8
						THRES[2:0]
Access						R/W	R/W	R/W
Reset						0	0	0


Bit	7	6	5	4	3	2	1	0
							PADFEN	FILT
Access							R/W	R/W
Reset							0	0

Bits 10:8 – THRES[2:0] Digital Filter Threshold

Value	Description
0	No filtering applied on TWI inputs.
1–7	Maximum pulse width of spikes which will be suppressed by the input filter, defined in peripheral clock cycles.

Bit 1 – PADFEN PAD Filter Enable

Value	Description
0	PAD analog filter is disabled.
1	PAD analog filter is enabled. (The analog filter must be enabled if High-speed mode is enabled.)

Bit 0 – FILT RX Digital Filter

TWI digital input filtering follows a majority decision based on three samples from SDA/SCL lines at peripheral clock frequency.

Value	Description
0	No filtering applied on TWI inputs.
1	TWI input filtering is active. (Only in Standard and Fast modes)