Re: RCX sound circuit

Hi,

I haven't really got the first clue what you are talking about here, but I would
like to - any suggestions for reading up on this stuff?

Thomas


In lugnet.robotics, Philippe Hurbain wrote:
> Hello Mark,
>
>> Your circuit diagram checks out Philo, though a 47k resistor to ground 
>> should be
>> added to the processor connection.
>
> Quite possible as I obtained the schematics only with an ohmeter...
>
>>
>> I was wondering what the other NAND gate is used for.  Input pin 1 traces to
>> somewhere under the ROM.  Input pins 2 and 13 and output pin 12 disappear
>> elsewhere.
>
> I spent some time again with my ohmeter, here is the schematics for this part:
> http://www.brickshelf.com/gallery/Philo/RCX-comp/motor_cmd.gif
>
> This is the motor driver control circuitry, data is latched when there is a
> write to address x111 xxxx xxxx xxxx (binary). As I think H8 is used in mode 
> 2,
> A15 is always 1 for external access, so any write to fxxx should write to 
> motor
> driver latches. In the schematics, OUT_X_1 and OUT_X_2 are connected to 
> Melexis
> motor drivers in1 and in2.
>
>> I suggest that a 3-input NAND gate was needed by the main computer circuit 
>> and
>> that the speaker driver circuit just mopped up the spare gates.
> Probably, yes ;o)
>
> Philo