RICHARD said:
Post a schematic of the circuit in the question; on
news:alt.binaries.schematics.electronic .
Dear me! I have never used alt.binaries.schematics.electronic before,
so I think I would just cause too much trouble asking how to do it. I
am so ashamed of myself, I am sorry.
.... I sure would, I am sorry ...
I think I could set up a small FTP dir on one of my
websites, where you could upload it.
Oh dear! I simply meet all the most wonderful people here on Usenet.
THANK YOU VERY MUCH INDEED. Again, I would not know how to FTP. Shame
on me.
Thank you very much for the most encouraging words. You see, I have
learned a very nice notation for representing the logic gates
circuitry from another most kind and helpful person here on Usenet. If
you do not mind, I will use it to specify the circuitry in question.
(So, here goes.)
This is a set/reset D-type edge triggered flip-flop (all schematics
are due to Mr. C. Petzhold /Code/. The notation is due to another
genius who, I think, does not wish to be mentioned. I am most greatful
to/for both.)
.------------.
| |
RESET | .---. |
o-----------------o>| | |
.-------->|NOR|-. |
| .>| | | |
| | '---' | |
| .-|-------' |
| | | |
| | '-------. |
| | .---. | | .---.
SET | '-->| | | '>| | Q
o-------o-|----o--->|NOR|-o----->|NOR|-o-----o
| | | .->| | | .>| | |
| | .---' '---' | | '---' |
| | | | | .-|-------'
| | | | | | |
| | | | .--------' | '-------.
.---. | | | | | .---. | .---. |
CLK | | | | | | '->| | '-->| | | ~Q
o->|NOT|-|-|--o-|--->|NOR|-o-. .->|NOR|-o-----o
| | | '-------o>| | | '-|->| |
'---' | | | '---' | | '---'
| |.-|-------' |
| || | |
| || '-------. |
| || .---. | |
| |'-->| | | |
DATA | '--->|NOR|-' |
o--------|---------->| | |
| '---' |
'---------------------'
abbreviated as:
RESET.---.
o--| |
SET | | Q
o--| n |--o
CLK | | ~Q
o--| |--o
DATA | |
o--| |
| |
'---'
So, (for example) a 4-bit set/reset (natural binary code) counter
looks like this.
.-----. |
o->| | |this NAND gate serves as
|NAND |-o-. |the clock signal
.>| | | | |generator
| '-----' | | |(I have some doubts here, too)
'---------' | |
.-------------' |
|
| .-----. |
| .>| | |the lowest bit of the counter
o-| |NAND |-. |is simply
| '>| | | |the negated clock signal
| '-----' | |
| |
| |
| .---. | .---. .---.
.--->| | | .--->| | --->| |
|| | | | | | | | | |
.---->| 1 |--.|.---->| 2 |--. .---->| 3 |--.
||| | | |||| | | | || | | |
||'-->| |-o------->| |-o------->| |-o|
|| | | ||||| | | || || | | ||
|| .->| | ||||| .->| | || || .->| | ||
|| | '---' ||||| | '---' || || | '---' ||
|| '--------'|||| '--------'| || '--------'|
|| |||| | || |
|| |||| | || |
|| |||| | |'---------------o RESET NBC-3
|| |||| | '----------------o SET NBC-3
|| |||'------------------------------o RESET NBC-2
|| ||'-------------------------------o SET NBC-2
|'---------------------------------------------o RESET NBC-1
'----------------------------------------------o SET NBC-1
|| | | ?-o RESET NBC-0
.-------------------------------------------' ?-o SET NBC-0
| || |
| .----------------------'
| | ||
| | .-''--.
| | | |
V V V V
NBC-3 NBC-2 NBC-1 NBC-0 NBC=Natural Binary Code
So the counter should output:
NBC-3 NBC-2 NBC-1 NBC-0
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0
1 1 0 1
1 1 1 0
1 1 1 1 (here the counter will rewind)
0 0 0 0
0 0 0 1
0 0 1 0...
I intend to use this counter as an Instruction Pointer in an 8088
circuitry I am working on. The problem lies in setting/resetting the
lowest bit of this counter, i.e. the NBC-0 bit. (I have some other
doubts too, the one I mention is the primary one.)
I understand I am taking a lot of your time asking this question, so
thank you very very much for your interest.
All the best,
Tom