Maarten ter Huurne <[EMAIL PROTECTED]> wrote:
> Below is a proposal for a JoyNet cable for the PC parallel port. I already
> built one and it works well.
> It can be used for transferring files between PC and MSX, for debugging (PC
> logging everything which the MSXes send), by emulators that want to
> implement JoyNet functionality etc.
> Please tell me if this design is good. If it is generally accepted, it
> should be added to the standard.
>
> ==========================================================================
>
> JoyNet cable for PC parallel port
>
> Pin-layout:
> SEND (DIN5 /m) RECV (DIN5 /f)
>
> GND 5 -------------------------------------+--------------------- 5 GND
> D0 1 --------------------------------+ | +--------------- 1 D0
> D1 2 -----------------------------+ | | | +------------ 2 D1
> ACK 3 --------------------------+ | | | | | +--------- 3 ACK
> | | | | | | |
> | | | | | | |
> 10 3 2 18-25 13 12 4
>
> PC (DB25 /m)
>
> ==========================================================================
>
General rules for such connections:
Don't connect any OUTPUTS to other OUTPUTS. If one is given a
different signal level as the other output, you have a short circuit.
As output also go signals that can be PROGRAMMED to serve as outputs
(like the bi-directional data lines of the PC parallel port).
Open collector outputs (which can be forced low by the software,
but can't be forced high, only 'let go' high, like the Trigger A/B
signals on the MSX joystick port), CAN be connected to other open
collector outputs, but NOT to any other normal output. If the normal
output is made high, and the open collector output is forced low, you
would have a short circuit.
Don't connect normal outputs with any power supply (including
ground), only open collector outputs can be shorted with ground, if
desired.
Inputs can in principle be connected to any other signal.
Preferably, don't put any power supplies (other than ground) on
connectors like this: it is not allowed to connect the +5 supply of
one machine to the +5 of another machine, and a mistake in
connectors, or using the wrong cable, might produce nasty
results ;-(
It's okay to use available power supplies outside a computer (like
the +5 on the MSX joystick port), but try to keep these off any
connecting cables.
Last general rule: only connect signals that use the same signal
levels. So not RS-232 (can be from -15 to +15) to MSX joystick port
(using TTL (0-5 V) levels).
For the above proposal, this looks okay...
Greetings, Alwin Henseler ([EMAIL PROTECTED])
http://huizen.dds.nl/~alwinh/msx (MSX Tech Doc page)
http://www.twente.nl/~cce/index.htm (Computerclub Enschede)
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