4b4t PRTS for communication

Yokota Yu

PAM-3 is used in USB4 version 2(new I/O) and 100BaseTX(old type of ethernet). Ternary system has the margin against Binary system, which was calculated by log2(3)≃1.58 and can be applied to ECC. But ECC needs complicated system which includes CRC, a type of Linear Feedback Shift Register. LFSR consumes much of electricity when run at high frequency(for example, Giga-bit Ethernet). So I introduce simple and new type of PRTS(Pseudo-Random Ternary Sequence) with 4b4t and PAM3. I believe that 4b4t and PAM3 system can reduce system cost of computer communication.

*4b4t encode/decode table(disparity=-2/+2)*
Disparity was used only from D.6 to D.9.
When previous disparity was 0 and next nibble is D.6～D.9 then the transmitter can choose (+2)abcd or (-2)abcd.
In worst case, four + or four - was sent subsequently{D.5 (+2)D.9}.
name	DCBA	(-2)abcd	abcd	(+2)abcd
D.0	0000		0+00
D.1	0001		00+0
D.2	0010		000+
D.3	0011		+000
D.4	0100		+00-
D.5	0101		+0--
D.6	0110	00++		00--
D.7	0111	0+0+		0-0-
D.8	1000	+0+0		-0-0
D.9	1001	++00		--00
D.A	1010		-0++
D.B	1011		-00+
D.C	1100		-000
D.D	1101		000-
D.E	1110		00-0
D.F	1111		0-00
Idle		0000	0000	0000
Preamble		0+0-	0+0-	0+0-
Preamble		-0+0	-0+0	-0+0
Preamble		0-0+	0-0+	0-0+
Preamble		+0-0	+0-0	+0-0
NACK		+-+-	+-+-	+-+-
NACK		-+-+	-+-+	-+-+