Please title this page. (states.htm)

Busy /Ack Time

State	Action	bat	baT	bAt	bAT	Bat	BaT	BAt	BAT
1	Get next byte of data T=0.5us Release /Strobe, Assert Data	1	5	1a	2b	1	6	4
2	T=0.5us, Assert /Strobe, Assert Data	2	1	2c	6	5		3d	3
3	T=0.5us, Release /Strobe, Assert Data	5		3	4	3	4	3e	4f
4	T=10s, Release /Strobe and Data	5i		4h	1	5		4g	6
5	T=5ms, Release /Strobe and Data	5j	6	1k		5	5	4

a: bAt - Printer not Busy, has released /Ack, we assert data without /Strobe and wait .5us
- bat - Printer not busy but seems to be asserting /Ack, we keep data live and wait for a bit to let the printer catch up and allow for transient /Ack.
- baT - Printer still not busy but /Ack persisted. We go to wait for /Ack to clear and may skip a data byte? Was this an /Ack that we thought had ended but was just bouncing? Mabey 6 is a better entry.
- Bat - Printer busy and asserting /Ack, shouldn't we be at a 5? but if we are at 1, then we just started or we were at 5 and not busy while /Ack ended and has now restarted with Busy on again or at 4 after a long time of not busy and no /Ack and now the /Ack we were waiting for comes with a Busy?
- BaT - the Bat was not a transient so something is wrong.
- BAt - printer is busy, go to 4 to wait for a while. If printer is offline, we will probably time out. If printer goes online, we will get an /Ack and think that we have sent a byte. How do PC routines prevent data loss under this condition?
b: bAT - We have been waiting .5us, now its time to:
c: bAt - Printer still not Busy, /Ack released, we keep data on and assert /Strobe
- bat - why are we getting an /Ack? Wait to see if its a transient
- baT - the ack persisted, mabey the printer is just that fast.
- bAT - Timeout while expecting a busy in response to our /Strobe. Mabey this should be a 2 instead to just hold untill busy comes up or a 3 to just continue anyway
- Bat - why are we getting an /Ack and while Busy? Just wait for the ack to end.
d: BAt - We have a Busy from the printer in response to our /Strobe. Do we need to wait anyway? If so make this a 2 and move to 3 when BAT.
e: BAt - We can release /Strobe since the printer responded to it and just need to keep the data on for another .5us.
- bat - 5
- baT - 5
- bAt - 3
- bAT - 4
- Bat - 3
- BaT - 4
f: BAT - Data was kept up for .5us, now we can:
g: BAt - Release the data and wait for a long while to let the printer work.
h: bAt - The printer is finished working on the data, but has not yet acknowledged reciept
- bat
- baT
- bAT
- BAT
i: bat - The printer is asserting /Ack
j: bat - We believe we have sent a byte to the printer. Now we just wait for the /Ack to release
- baT
- Bat
- BaT
- BAt
- BAT
k: bAt - The /Ack is over, we can repeate the process.

	1	2	3	3	4	4	5
Busy	_	_	~	~	~	_	_
/Ack	~	~	~	~	~	~	_
/Strobe	~	_	_	~	~	~	~
Data	D	D	D	-	-	-	-

file: /Techref/io/parallel/states.htm, 6KB, , updated: 2008/3/18 10:57, local time: 2025/3/25 11:37,

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