6502.org

Lee...
There will be errors in this ... Ive been correcting it all night

To rotate the wrist requires two steppers that are rotated equally in opposite directions.. And to flex the wrist the same two steppers have to run in the same direction.. I don't think they implemented combination moves but I could be wrong, (by stepping one motor at a different count than the other would cause a flex and rotate at the same time)..
You probably picked this info up already from the partial manual on the ctrl-c website but I reiterate just in case it was missed..

The Teaching Pendant consisting 14 buttons probably monitored by 4 X 4 matrix polling routine,, But I could be wrong will have to disassemble the pendant to trace it out,, And the 5 LED's Seem to each have its own outputs,, And an additional user defined 5 TTL outputs on Plug P17.. NOTE the pendant has nothing but the 14 switches in it,, And the 5 LED's with current limiting resistors.. That plugs into the P15 Header.. I have yet to map the pendant..

There are leftover Hex Inverters on the 74LS14 Clock/Reset circuit that are used in address decoding.. One pair double inverts phi-2 for delay line of 30 to 44ns,, And the other inverts A15 Address to CS\ on the 2732A Eprom..

74LS251 handles 9 inputs, 7 User Inputs plus one combined Pendant & Gripper tension micro-switch input paired to a single input.. My guess the E-Stop button is the one paired with the gripper...

Keyboard is 14 keys minus 1 are probably on a 4X4 Matrix so (4 in) (4 out) Plus (5 out) for the LED's And another (5 out) on P17 for User outputs,, Total 18
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P17 user I/O ?? The 74LS251 output is tri-state and toggles D7, But I can't see where it's output is being limited to the read cycle only...
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pins 2 & 15 P17 GND and Pin 1 = +5
pin 15 = I4 < pin 10 P17 User Optional Input
pin 14 = I5 < pin 12 P17 User Optional Input
pin 13 = I6 < pin 14 P17 User Optional Input
pin 12 = I7 < pin 16 P17 User Optional Input
pin 01 = I3 < pin 08 P17 User Optional Input
pin 02 = I2 < pin 06 P17 User Optional Input
pin 03 = I1 < pin 04 P17 User Optional Input
pin 04 = I0 < pin 12 P15 Pendant & P16 Gripper SW
Pin 05 = Z\ > NC or not found
pin 06 = Z > pin 26 on CPU & VIA - D7
pin 07 = E1 < pin 09 74LS138 Addressing
pin 09 = S2 < pin 11 cpu - A2
pin 10 = S1 < pin 10 cpu - A1
pin 11 = S0 < pin 09 cpu - A0
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R6502A CPU Pins with * have pull-up resistor
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pin 4 = IRQ *
pin 6 = NMi *
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VIA 6522 Pins with * have pull-up resistor
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pin 35 RS3 < A3 cpu
pin 36 RS2 < A2 cpu
pin 37 RS1 < A1 cpu
pin 38 RS0 < A0 cpu
pin 24 CS1 < pin 23 A13 cpu
pin 23 CS2 < pin 25 A15 cpu
pin 40 CA1 - single pin header E4 NC
pin 39 CA2 - single pin header E5 NC
pin 18 CB1 - single pin header E7 NC
pin 19 CB2 > pin 03 & 04 ACIA U13 & U15 RX & TX Clock
pin 25 Phi-2 < pin 12 LS14 delayed Phi-2 30 to 44ns
pin 34 Res < pin 40 cpu = Reset
pin 22 R/W <pin 34 cpu = R/W
pin 21 IRQ >pin 06 cpu = NMI *
pin 02 PA0 < pin 01 P15 pendant *
pin 03 PA1 < pin 02 P15 pendant *
pin 04 PA2 < pin 03 P15 pendant *
pin 05 PA3 < pin 04 P15 pendant *
pin 06 PA4 < pin 05 P15 pendant *
pin 07 PA5 < pin 06 P15 pendant *
pin 08 PA6 < pin 07 P15 pendant *
pin 09 PA7 - pin NC or not found *
pin 10 PB0 < pin Baud Dip Switch 1 *
pin 11 PB1 < pin Baud Dip Switch 2 *
pin 12 PB2 < pin Baud Dip Switch 3 *
pin 13 PB3 < pin Baud Dip Switch 4 *
pin 14 PB4 > pin 10 P15 pendant
pin 15 PB5 > pin 11 P15 pendant
pin 16 PB6 - pin NC or not found
pin 17 PB7 - single pin header E6 NC
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68B50 ACIA Addressing & Clock U13 & U15 Are the same except for pin 09 = CS2\
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pin 07 = IRQ > pin 04 cpu
pin 08 = CS0 < pin 24 cpu
pin 09 = CS2\------ ACIA U13 pin 09 < pin 22 = A12 cpu ------ ACIA U15 pin 09 < pin 20 = A11 cpu
pin 10 = CS1 < pin 08 74LS14
pin 11 = RST < pin 09 cpu
pin 13 = R/W < pin 34 cpu
pin 14 = ENA < pin 12 74LS14 Delayed phi-2
pin 03 & 04 = RX & TX clock < pin 19 = CB2 on U19 VIA
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74LS14 is the standard Clock & Reset circuit
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Pins 1-2-3-4 Crystal & Clock (Crystal & Caps now removed and pin 1 driven by a 1.8432mhz crystal oscillator)
Pins 5-6 Power on Reset circuit
pin 09 < pin 25 A15 6502
pin 08 > pin 20 on 28 pin eprom socket which is pin 18 on the 2732 CE\
pin 11 < pin 39 6502 Phi-2 out
Pin 10 > pin 13 input LS14
pin 12 > pin 25 VIA -- pin 06 = E3 74LS138 -- pin14 = Ena ACIA U13 & U15 ((Delayed Phi-2 30 to 44ns))
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74LS138 address decoding.. seems their using Phi2 as part of the decoding
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pin 01 = A0 < A10 cpu
pin 02 = A1 < A11 cpu
pin 03 = A2 < A12 cpu
pin 04 = E1 < A14 cpu
pin 05 = E2 < A15 cpu
pin 06 = E3 < pin 12 74LS14 Delayed Phi-2
pin 15 = 0 > pin 08 U16 & U17 first 1k of ram
pin 14 = 1 > pin 08 for piggybacked second 1k of ram from the E1 single tie point
pin 13 = 2 > pin 09 74LS174 U12 Base U11 and 1/2 Shoulder U07
pin 12 = 3 > pin 09 74LS174 U05 Elbow U04 and 1/2 Shoulder U07
pin 11 = 4 > pin 09 74LS174 U09 R-Wrist U10 and 1/2 L-Wrist U06
pin 10 = 5 > pin 09 74LS174 U02 Gripper U03 and 1/2 L-Wrist U06
pin 09 = 6 > pin 07 74LS251 U23
pin 07 = 7 > pin 14 74LS259 U22

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74LS259 Addressable Latch
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pin 01 = A1 < pin 09 cpu A0
pin 02 = A2 < pin 10 cpu A1
pin 03 = A3 < pin 11 cpu A2
pin 04 = Q0 > pin 14 of P15 pendant
pin 05 = Q1 > pin 13 of P17 user
pin 06 = Q2 > pin 11 of P17 user
pin 07 = Q3 > pin 09 of P17 user
pin 09 = Q4 > pin 07 of P17 user
pin 10 = Q5 > pin 05 of P17 user
pin 11 = Q6 > pin 09 of P15 pendant
pin 12 = Q7 > pin 13 of P15 pendant
pin 13 = D < pin 33 cpu D0
pin 14 = E\ < pin 07 74LS138 Addressing
pin 15 = C\ < pin 40 cpu Reset
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UDN5707A Each of the 4 NAND gates have their inputs paired to a single single 74LS174 output
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74LS174 Map to UDN5707A Drivers Inputs U03, U04, U06, U07, U10, U11 Still Have to Map the driver out to the motor coil..

Now that I Know the NAND gates are negated by tying the two inputs together,, I can socket all the UDN5707A's and replace them with ULN2803 darlington arrays with a little lead swapping on a dip headers to replace the smoked outputs.. A whole lot cheaper than the $35 to $40 the get for the original drivers..
The six Steppers are Unipolar six wire dual stack tin-can type,, Rated at 12v 35 ohms 7.5 deg step.. The outer stack has yellow and orange leads with Red common to +12v,, And the Inner stack has Black and Brown leads with Red common to +12v... The driver chips are open Collector with integral protection diodes, And sink to GND..
------------------
U02 pin 09 < pin 10 74LS138
U02 pin 02 > U03 pin 15 & 14 Grip ----- output on pin 13 P14 Brown
U02 pin 05 > U03 pin 12 & 11 Grip ----- output on pin 10 P13 Yellow
U02 pin 07 > U06 pin 15 & 14 L-Wrist -- output on pin 13 P12 Orange
U02 pin 10 > U06 pin 02 & 01 L-Wrist -- output on pin 03 P12 Yellow
U02 pin 12 > U03 pin 06 & 05 Grip ----- output on pin 07 P13 Orange
U02 pin 15 > U03 pin 02 & 01 Grip ----- output on pin 03 P14 Black
------------------
U05 pin 09 < pin 12 74LS138
U05 pin 02 > U04 pin 02 & 01 Elbow ---- output on pin 03 P07 Black
U05 pin 05 > U04 pin 12 & 11 Elbow ---- output on pin 10 P07 Brown
U05 pin 07 > U04 pin 06 & 05 Elbow ---- output on pin 07 P08 Orange
U05 pin 10 > U07 pin 02 & 01 Shoulder - output on pin 03 P06 Brown
U05 pin 12 > U07 pin 15 & 14 Shoulder - output on pin 13 P06 Black
U05 pin 15 > U04 pin 15 & 14 Elbow ---- output on pin 13 P08 Yellow
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U09 pin 09 < pin 11 74LS138
U09 pin 02 > U10 pin 15 & 14 R-Wrist -- output on pin 13 P09 Yellow
U09 pin 05 > U06 pin 06 & 05 L-Wrist -- output on pin 07 P11 Black
U09 pin 07 > U06 pin 12 & 11 L-Wrist -- output on pin 10 P11 Brown
U09 pin 10 > U10 pin 12 & 11 R-Wrist -- output on pin 10 P09 Orange
U09 pin 12 > U10 pin 06 & 05 R-Wrist -- output on pin 07 P10 Brown
U09 pin 15 > U10 pin 02 & 01 R-Wrist -- output on pin 03 P10 Black
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U12 pin 09 < pin 13 74LS138
U12 pin 02 > U11 pin 15 & 14 Base ----- output on pin 13 P04 Yellow
U12 pin 05 > U11 pin 12 & 11 Base ----- output on pin 10 P04 Orange
U12 pin 07 > U11 pin 06 & 05 Base ----- output on pin 07 P03 Brown
U12 pin 10 > U07 pin 06 & 05 Shoulder - output on pin 07 P05 Yellow
U12 pin 12 > U07 pin 12 & 11 Shoulder - output on pin 10 P05 Orange
U12 pin 15 > U11 pin 02 & 01 Base ----- output on pin 03 P03 Black

Big Time Stuck
I can find no connection between the 6502, Or any other chip connected to the six data inputs on any of the four 74LS174's .. All the outputs mapped ok and reset to pin40 on the cpu and the clock all traced out to the LS138.. But connected from the data pins on the LS174 I dragged my meter probe over every pin and IC on the board without a peep from my meter.. I'm completely stymied ..

Anybody have any ideas
I

UPDATE added 9-2011 I put it here to keep all wiring info in the same place..I finally got all the motor leads marked so I could complete the board removal...
And I found a hidden chip glued to the bottom of the board..

________________________________________________
74LS174 Data Inputs , Inverted Data Buss from 74LS540 Hidden Chip Uxx
----------------------------
U02 pin 03 < y4 = D3\
U02 pin 04 < y2 = D1\
U02 pin 06 < y8 = D7\
U02 pin 11 < y7 = D6\
U02 pin 13 < y1 = D0\
U02 pin 14 < y3 = D2\
----------------------------
U05 pin 03 < y1 = D0\
U05 pin 04 < y2 = D1\
U05 pin 06 < y3 = D2\
U05 pin 11 < y8 = D7\
U05 pin 13 < y7 = D6\
U05 pin 14 < y4 = D3\
----------------------------
U09 pin 03 < y2 = D1\
U09 pin 04 < y5 = D4\
U09 pin 06 < y6 = D5\
U09 pin 11 < y1 = D0\
U09 pin 13 < y4 = D3\
U09 pin 14 < y3 = D2\
----------------------------
U12 pin 03 < y4 = D3\
U12 pin 04 < y3 = D2\
U12 pin 06 < y2 = D1\
U12 pin 11 < y6 = D5\
U12 pin 13 < y5 = D4\
U12 pin 14 < y1 = D0\

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74LS541 Tri-State Octal Buffer Driver (hidden Chip Glued to bottom of PCB
-----------------------------------------
Uxx pin 01 = E1 < GND Both Enables Tied Low, Chip is always active
Uxx pin 19 = E2 < GND
--------------------
uxx pin 02 = D1 < D0
uxx pin 03 = D2 < D1
uxx pin 04 = D3 < D2
uxx pin 05 = D4 < D3
uxx pin 06 = D5 < D4
uxx pin 07 = D6 < D5
uxx pin 08 = D7 < D6
uxx pin 09 = D8 < D7
---------------------
uxx pin 18 = y1 > U02 pin 13, U05 pin 03, U09 pin 11, U12 pin 14
uxx pin 17 = y2 > U02 pin 04, U05 pin 04, U09 pin 03, U12 pin 06
uxx pin 16 = y3 > U02 pin 14, U05 pin 06, U09 pin 14, U12 pin 04
uxx pin 15 = y4 > U02 pin 03, U05 pin 14, U09 pin 13, U12 pin 03
uxx pin 14 = y5 > U09 pin 04, U12 pin 13

YES. Perhaps the inputs are limit switch buffering holders? Do the inputs connect to the pins out to the robot or pendant? The outputs are connected through another port to the data bus chain? this has the debounce advantage that any switch activation is held in the 174 as memory until the CPU is ready to read the switch. this way, the program does not have to continuously poll it?

Making sure I understand: you're trying to determine the origin for the signals that drive the six D inputs of each '174 flipflop. And the D outputs of the four '174s are what drive the NAND inputs of the stepper-driver ICs -- right?

Not sure why your meter fails to trace these, but it's very likely the D inputs come from the system data bus -- or (less likely) the address bus. Also I expect some of the D inputs share a common origin; ie, some of the Ds connect to one another; can you verify that?

Is your oscilloscope handy? By probing those D inputs you could "sniff" the signals and compare with what appears at points elsewhere on the board -- including the buses, as I say. I admit that may seem like a shot in the dark. But myself when I'm stymied I like to shift the perspective and try to look at some new information. Hope that helps... keep us posted

-- Jeff

From the code it would seem four of the inputs for all four 74LS174s go to d0-d3 and a pair of bits from U12 and U09 go to two of d7-d4 and a pair of bits from U05 and U02 go to the other two of d7-d4.

I'm addding the I/O and address info to the disassembly.

Lee.

The keys are on a 2 x 7 matrix.

I've guessed how some of the LEDs are driven.

The disassembly has been updated.

Lee.

Thanks Everyone,,
I have it pretty well torn apart right now,, I started de-soldering the driver chips because 2 of them are toast and I want to socket the board.. So I can't do powered testing right now.. It's limited to poking traces with my trusty Extech meter its 4 1/2 digit hi-end unit,, It will give me readings in Milli-ohms so I can trust what readings i am getting.. Although I will admit tapping the probes together many times to make sure it was still working when I couldn't find any data connections...


Tony.. They directly drive the stepper driver chips and have to produce the stepper coil drive pattern,, Each has its own address decoded by the 74LS138 connected to pin 9 the clock/latch input And the data inputs should be on the cpu data buss, But my meter keeps reading infinity Going to have another go at it tonight.. All motors are half-stepped in a 1-coil, 2-coil, 1-coil pattern,, Each driver controls 1 motor but each LS174 controls 1-1/2 driver chips.. why they didn't use 8bit data bus latches is totally beyond me .. Maybe they just had a crap-load of LS174's sitting on a shelf they wanted to get rid of..

Lee.. Also Thanks
The 2 x 7 matrix makes sense,, I pulled the back off the pendant again and from the bottom side or the PCB what traces I can see tend to verify 2 x 7 .. I'm going to take another go at the LS174's D inputs in a while after I scan through your latest version of the dis-assembly .. And look for the interconnects you gleaned from from it.. The LED's could be be part of the multiplexing scheme but till I trace the pendant I'm just guessing,, The ribbon cable to the pendant is 16 conductor 2 x 7 uses 9 of them.. 1 is probably grounding the case.. I will have to check to see if any more of the LS251 leads are paired with any of the pendant leads,, I stopped checking when I found a single connection, will double check for additional pairing ,, That may be what is used to poll the 2 columns of the keyboard array.. Minor Note: pins on P17 User option plug are numbered like a IC but P15 pendant are numbered odd even..

Found The Problem,, A Hidden 74LS540 inverting tri-state buffer,, Glued to bottom of board 6 traces are cut and its wired between data bus and the LS174's I'm adding the trace info to the earlier post to keep all the wiring info together ... Both enable chips are tied to GND so the chip is always active..

I had the board all but out for 2 days but needed to mark all the motor leads before I could pull it .. wasn't in a hurry because the order for the 16 pin machined sockets had not arrived yet .. but still reading infinity forced me to finish board removal and SURPRISE!! .. I'm almost afraid to touch it wire-wrap wire tacked to traces.. If one breaks off will play hell trying to find out where it was connected.. I only found 6 traces cut but they are feeding all 8 data bits into the various LS174's with 14 jumpers on the data out side..

Update............................

Lee... You got this one right on the wiring pattern,, You just didn't predict the inverted data buss.. Well all the major circuitry is mapped just need to do the pendant, And the serial ports but that should be pretty standard.. Then map out some of the W_ jumpers, And the E_ tie points..

That explains a lot, like why the bit patterns for energizing the motors seemed to be inverted.
I'm guessing they originally wired all the '174s to the same six data lines but found some problem with writing the motor patterns that way.

Lee.

If you replace all the UDN5707As with ULN2803s you can replace the 74LS540 with a 74LS541 to save the extra inverters. It will also mean that the reset inputs on the '174s will turn all the motor outputs off instead of turning them on so you could connect the '174 resets to the CPU reset.

Lee.

Yes that's true. There's also another option.

I was wondering why the inverting buffer got kludged in there, and I think it may have been in response to difficulties sourcing parts. My hunch is that the original design specified that noninverting stepper driver ICs be used; both UDN5703A and '06A (OR & AND inputs, respectively) would be OK, but perhaps these chips were temporarily unobtainable. As a workaround solution, hacking in the 'LS540 allowed a substitution to be made; it allowed both UND5733A and '07A (inverting NOR & NAND inputs) to fill the bill instead. (An alternative workaround would have been to modify the stepper routines in the EPROM.)

Now you plan on replacing the stepper-driver ICs, and this implies an opportunity. You will have a sturdier and more serviceable board if you remove the fragile 74LS540 wiring and restore the original PCB connections that were severed. Of course the other result is that you will need to shop for noninverting stepper drivers, not inverting -- and that might work out very much in your favor as well! I don't know what's available these days, but perhaps you could find a cheap source of UDN5703A or '06A, or an equivalent IC that uses the original pinout; that would be a real advantage.

Lee is correct about the Reset issue, so perhaps there's another kludge that needs to be undone; I need to do some head scratching about that.

(BTW, as to the earlier question of why '174 type hex flipflops were used, that may be a parts procurement issue as well. Given the age of the PCB's design, perhaps the supply of the new octal devices such as 'LS374 was considered too iffy.)

-- Jeff

The 174's reset does go directly to the cpu pin 40...

Which means during power on reset all the 174's outputs are low and remain so till the processor initializes them..
Whatever I do I have to avoid all the drivers sinking current and energizing every coil on every stepper during this period,, Otherwise it will draw a huge current.. At 13.8 volt from the 10 amp Astron power supply which is what they were shipping the robots with,, It comes to around 9 amps,, Far in excess of anything drawn during normal operation...

Allegro has discontinued all the 57xx series and most of the 25xx series drivers,, And to procure any comes at a ridiculous price.. And at only 300ma per output, they are very marginal for what they are asked to do, At 13.8 volts drop off .6 volt for the input reverse polarity protection diode and each stepper at 35 ohms per coil draws 377ma.. The question is do I try to rework whats on the board, Or do I build a daughter board and just feed the 4 addressing lines and the 8bit data bus to it and design from scratch a new driver circuit.. Another option would be to rewrite the code to provide step and direction signals, And that opens things up to a wide variety of new chips.. Was thinking about the UCN5804B but that has also been discontinued as has most dip package products.. But this one is still available at reasonable prices and offers multiple stepping modes... The question is do I try to keep it vintage or modernize it...

But being they already hacked their own product leaves me less than satisfied with the status qua.. For a Robot Arm they were selling for $3500.00 in the 80's, They sure cut allot of corners to keep the board cost low..
I'm open to Ideas Here..

In normal operation it's possible for each motor to have as many as two coils active. Thus, having all four coils active represents only double the usual worst-case load -- a condition that's readily tolerable, assuming it only lasts a second or two. In other words I don't think there's any threat of your unit going up in smoke. But, besides avoiding smoke, there's another issue.
Hmmm.. I have some doubts about this. It would be true if the CPU RST pin was low immediately from the instant of powerup, but I suspect it's not the case. The NMOS 6502 (unlike most CPUs, including 65C02) is prohibited from long periods with RST true [Edit: this point is now considered false or at least highly questionable], and therefore a one-shot timing circuit is usually provided. So, there is no RST until the one-shot pulse commences.
Question: is this connection to pin 40 part of the original PCB, or is it one of the wire mod's? The '174s should reset before the 6502. Because...

• - at powerup the 174s could "wake up" in any state.
  - the CPU won't reset until well after the power supply voltage has stabilized (and the one-shot pulses commences)
  - therefore the 174s have not been reset -- and the 100% overload could prevail! -- during the delay that's provided for the power supply voltage to stabilize.

Unfortunately, in the presence of an overload, the voltage might not stabilize as expected. The result might be intermittent starting of the robot -- which is something you mentioned experiencing! That's why I'm curious about the signal driving the '174 resets.

-- Jeff

I'm concerned the drivers are already operating 77ma over their rated current... With all four sinking on the same chip that's 308ma added to the package dissipation.. It may not smoke them but it sure shortens their life..

The CPU is a 2mhz rockwell

This is not a one-shot circuit, It has a 47uf cap in the reset circuit,, I did not check the resistor value so not sure what the time constant is.. And unless I'm in error here, Reset stays low from the time the power is turned on till the cap charges through the resistor and reaches the gate threshold of the 74LS14 which is a double inverted signal so a low on the cap is low on the cpu,, At the threshold reset pin 40 goes high and the cpu initializes.. Which would also hold the 174's in reset which sets all outputs low till the cpu addressed them and placed a value in the flip-flops..

Anyways the original design prevent the high current situation The 5707 truth table is L+L = H which means the output transistors are turned off..
Also the ULN2803A has the same truth table a L=H so the transistor is also off...So no problem there..
Just wondering what the original problem was with the stepper code that made them have to invert the signal.