DCC State Machine 004

DCC State Machine version 004

State 0 is to synchronize on the preamble. It is initiated with DCC_subst set to 0.

Condition	Action	Process	Next state
receive 0 bit	if DCC_subst < 20 set DCC_subst to 0 ELSE set DCC_subst to 8 and go to state 1	dca02 -> dca03	0 1
receive 1 bit	increment DCC_subst	dca04	0

State 1 verifies the second half of a "0" bit

Condition	Action	Process	Next state
receive 0 bit	if DCC_subst == 0 go to state 4, else go to state 2 for next bit	dca07	2 / 4
receive 1 bit	set DCC_subst to 0, go to state 0	dca01	0

State 2 processes the first half of a bit

Condition	Action	Process	Next state
receive 0 bit	assemble "0" bit, decrement DCC_subst, go to state 1 to verify	dca05	1
receive 1 bit	assemble "1" bit, decrement DCC_subst, go to state 3 to verify	dca06	3

State 3 verifies the second half of a "1" bit

Condition	Action	Process	Next state
receive 0 bit	set DCC_subst to 0, go to state 0	dca01	0
receive 1 bit	if DCC_subst == 0 go to state 4, else go to state 2 for next bit	dca07	2 / 4

State 4 looks for EOM or start another byte

Condition	Action	Process	Next state
receive 0 bit	set DCC_subst to 8, go to state 1	dca03	1
receive 1 bit	set EOM, check checksum if used / set DCC_subst to 0 go to state 0	dca00 -> dca01	0

Proc	Condition	Action
dca00		set EOM, check checksum if enabled. Fallthrough to dca01
dca01		set DCC_subst to 0, go to state 0
dca02	DCC_subst < 20 ELSE	set DCC_subst to 0, stay in state 0 fall through to dca03
dca03		set DCC_subst to 8, go to state 1 to verify
dca04		increment DCC_subst, stay in state 0
dca05		assemble 0, decrement DCC_subst, go to state 1 to verify
dca06		assemble 1, decrement DCC_subst, go to state 3 to verify
dca07	DCC_subst == 0 ELSE	process byte, go to state 4 go to state 2 for next bit