SEQ - Sequencer

The sequencer block performs automatic execution of sequenced lines to produce timing signals. Each line optionally waits for an external trigger condition and runs for an optional phase1, then a mandatory phase2 before moving to the next line. Each line sets the block outputs during phase1 and phase2 as defined by user-configured mask. Individual lines can be repeated, and the whole table can be repeated, with a value of 0 meaning repeat forever.

Fields

Name	Type	Description
ENABLE	bit_mux	Stop on falling edge, reset and enable on rising edge
BITA	bit_mux	BITA for optional trigger condition
BITB	bit_mux	BITB for optional trigger condition
BITC	bit_mux	BITC for optional trigger condition
POSA	pos_mux	POSA for optional trigger condition
POSB	pos_mux	POSB for optional trigger condition
POSC	pos_mux	POSC for optional trigger condition
TABLE	table	Sequencer table of lines REPEATS Number of times the line will repeat TRIGGER The trigger condition to start the phases POSITION The position that can be used in trigger condition TIME1 The time the optional phase 1 should take OUTA1 Output A value during phase 1 OUTB1 Output B value during phase 1 OUTC1 Output C value during phase 1 OUTD1 Output D value during phase 1 OUTE1 Output E value during phase 1 OUTF1 Output F value during phase 1 TIME2 The time the mandatory phase 2 should take OUTA2 Output A value during phase 2 OUTB2 Output B value during phase 2 OUTC2 Output C value during phase 2 OUTD2 Output D value during phase 2 OUTE2 Output E value during phase 2 OUTF2 Output F value during phase 2 15:0 REPEATS 19:16 TRIGGER enum 0 Immediate 1 BITA=0 2 BITA=1 3 BITB=0 4 BITB=1 5 BITC=0 6 BITC=1 7 POSA>=POSITION 8 POSA<=POSITION 9 POSB>=POSITION 10 POSB<=POSITION 11 POSC>=POSITION 12 POSC<=POSITION 63:32 POSITION int 95:64 TIME1 20:20 OUTA1 21:21 OUTB1 22:22 OUTC1 23:23 OUTD1 24:24 OUTE1 25:25 OUTF1 127:96 TIME2 26:26 OUTA2 27:27 OUTB2 28:28 OUTC2 29:29 OUTD2 30:30 OUTE2 31:31 OUTF2
PRESCALE	param time	Prescalar for sequencer table times
REPEATS	param	Number of times the table will repeat
ACTIVE	bit_out	Sequencer active flag
OUTA	bit_out	Output A for phase outputs
OUTB	bit_out	Output B for phase outputs
OUTC	bit_out	Output C for phase outputs
OUTD	bit_out	Output D for phase outputs
OUTE	bit_out	Output E for phase outputs
OUTF	bit_out	Output F for phase outputs
TABLE_REPEAT	read	Current iteration through the entire table
TABLE_LINE	read	Current line in the table that is active
LINE_REPEAT	read	Current iteration of the active table line
STATE	read enum	Internal state machine state 0 UNREADY 1 WAIT_ENABLE 2 WAIT_TRIGGER 3 PHASE1 4 PHASE2
HEALTH	read enum	Was last run successful? 0 OK 1 DMA underrun 2 Not ready for table

Sequencer Table Line Composition

Bit Field	Name	Description
[15:0]	REPEATS	Number of times the line will repeat
[19:16]	TRIGGER	The trigger condition to start the phases 0: Immediate 1: BITA=0 2: BITA=1 3: BITB=0 4: BITB=1 5: BITC=0 6: BITC=1 7: POSA>=POSITION 8: POSA<=POSITION 9: POSB>=POSITION 10: POSB<=POSITION 11: POSC>=POSITION 12: POSC<=POSITION
[63:32]	POSITION	The position that can be used in trigger condition
[95:64]	TIME1	The time the optional phase 1 should take
[20:20]	OUTA1	Output A value during phase 1
[21:21]	OUTB1	Output B value during phase 1
[22:22]	OUTC1	Output C value during phase 1
[23:23]	OUTD1	Output D value during phase 1
[24:24]	OUTE1	Output E value during phase 1
[25:25]	OUTF1	Output F value during phase 1
[127:96]	TIME2	The time the mandatory phase 2 should take
[26:26]	OUTA2	Output A value during phase 2
[27:27]	OUTB2	Output B value during phase 2
[28:28]	OUTC2	Output C value during phase 2
[29:29]	OUTD2	Output D value during phase 2
[30:30]	OUTE2	Output E value during phase 2
[31:31]	OUTF2	Output F value during phase 2

Generating fixed pulse trains

The basic use case is for generating fixed pulse trains when enabled. For example we can ask for 3x 50% duty cycle pulses by writing a single line table that is repeated 3 times. When enabled it will become active and immediately start producing pulses, remaining active until the pulses have been produced:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
3	Immediate	0	5	1	0	0	0	0	0	5	0	0	0	0	0	0

We can also use it to generate irregular streams of pulses on different outputs by adding more lines to the table. Note that OUTB which was high at the end of Phase2 of the first line remains high in Phase1 of the second line:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
2	Immediate	0	5	1	0	0	0	0	0	2	0	1	0	0	0	0
3	Immediate	0	1	1	1	0	0	0	0	2	0	0	0	0	0	0

And we can set repeats on the entire table too. Note that in the second line of this table we have suppressed phase1 by setting its time to 0:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
2	Immediate	0	5	1	0	0	0	0	0	2	0	0	0	0	0	0
1	Immediate	0	0	0	0	0	0	0	0	5	0	1	0	0	0	0

There are 6 outputs which allow for complex patterns to be generated:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	3	1	0	0	0	0	0	4	1	1	0	0	0	0
1	Immediate	0	5	1	1	1	0	0	0	6	1	1	1	1	0	0
1	Immediate	0	7	1	1	1	1	1	0	8	1	1	1	1	1	1

Statemachine

There is an internal statemachine that controls which phase is currently being output. It has a number of transitions that allow it to skip PHASE1 if there is none, or skip WAIT_TRIGGER if there is no trigger condition.

External trigger sources

The trigger column in the table allows an optional trigger condition to be waited on before the phased times are started. The trigger condition is checked on each repeat of the line, but not checked during phase1 and phase2. You can see when the Block is waiting for a trigger signal as it will enter the WAIT_TRIGGER(2) state:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
3	BITA=1	0	2	1	0	0	0	0	0	1	0	0	0	0	0	0
1	BITB=1	0	3	0	1	0	0	0	0	2	0	0	0	0	0	0

You can also use a position field as a trigger condition in the same way, this is useful to do a table based position compare:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	POSA>=POSITION	20	0	0	0	0	0	0	0	4	0	1	0	0	0	0
3	Immediate	0	1	1	1	0	0	0	0	3	0	1	0	0	0	0
2	POSA<=POSITION	10	1	1	0	0	0	0	0	3	0	0	0	0	0	0

Prescaler

Each row of the table gives a time value for the phases. This value can be scaled with a block wide prescaler to allow a frame to be longer than 2**32 * 8e-9 = about 34 seconds. For example:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
2	Immediate	0	1	1	0	0	0	0	0	1	0	0	0	0	0	0

Interrupting a sequence

Setting the repeats on a table row to 0 will cause it to iterate until interrupted by a falling ENABLE signal:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
0	Immediate	0	5	1	0	0	0	0	0	5	0	0	0	0	0	0

In a similar way, REPEATS=0 on a table will cause the whole table to be iterated until interrupted by a falling ENABLE signal:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	0	0	0	0	0	0	0	5	1	0	0	0	0	0
2	Immediate	0	0	0	0	0	0	0	0	3	0	0	0	0	0	0

And a rising edge of the ENABLE will re-run the same table from the start:

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	5	1	0	0	0	0	0	5	0	0	0	0	0	0

Streaming tables

When TABLE_LENGTH has the most significant bit set, it indicates there will be one more table pushed. The condition in which a new table can be pushed is signaled via an interrupt. When the last table is pushed (indicated by TABLE_LENGTH’s most significant bit cleared), the sequencer will repeat that table according to the value of the REPEATS register.

(Source code, png, hires.png, pdf)

T1
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	0	0	0	0	0	0	0	20	1	0	0	0	0	0
1	Immediate	0	0	0	0	0	0	0	0	20	0	0	0	0	0	0

T2
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	0	0	0	0	0	0	0	20	0	1	0	0	0	0
1	Immediate	0	0	0	0	0	0	0	0	10	0	0	0	0	0	0
1	Immediate	0	0	0	0	0	0	0	0	10	0	0	0	0	0	0

T3
#	Trigger		Phase1	Phase1 Outputs						Phase2	Phase2 Outputs
Repeats	Condition	Position	Time	A	B	C	D	E	F	Time	A	B	C	D	E	F
1	Immediate	0	0	0	0	0	0	0	0	20	0	0	1	0	0	0