Posted By
MMS
on 2016-12-27
09:34:46
 |  Re: PC RS232 Mouse project for Plus/4 User port_a cheap and working one :-)
OFFs (it is nice feeling to make my own topic offtopic, haha  )
-Actually the two userports are different, but it seems for serial port (RS232 style in TTL) communication they are *almost* pin equivalent.
Question remains:
What will the connection to B line cause in Plussy? (I checked the circuit diagram of the VIC-1011A, it happens)
On C64 B is the Flag bit for CIA, and the C is the Data0 (of the 8 paralell data bits). Hm.
In our case B is the Data0 (will be not used for serial transfer) but as a ACIA manages an IRQ when data (level) appears on pin C (Receive data). Seem they will behave the same way, even if a C64 RS232 or modem card connected to Plus/4.
It could happen, that C64 Commodore modems and RS232 interfaces are 100% Plus/4 compatible?
-In the V3 version of the document I will add the RXD connection to userport, and the MAX232 IC pin layout too, in case somone wants to built his/her own.
By this, the interface will be a full I/O RS232 device (from hardware point of view).
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