[comp.sys.cbm] How to program the userport of the CBM Plus4-computer??

brouw@dutesta.UUCP (Gerard Brouwer) (02/29/88)

Four weeks ago I posted the following message. However I was unable to
read (if there were any) the replies, so I decided to post it again.
Here is the message again:

The newsgroup 'comp.sys.cbm' contains a lot of information for the
C-128 and C-64 computers. I wondered if there are also users of
different types of Commodore-computers, especially the family of
C-116, C-16, C-232 and Plus4.

I find it difficult to get detailed information about this family,
so here are my questions:

- I want to use the User-port of the Plus4 for I/O.
  There are two parts:
  Part 1: RS-232 interface connections.
  Part 2: 8 databits and other connections.

  The 8 databits are easy to program for output:
     LDA <data>
     STA $FD10
  But what about input?
  Is there a Data Direction Register (like a C-64)?

- What is the influence of the ACIA to the User-port?
  The ACIA has four registers:
     1 - Command register
     2 - Status  register
     3 - Data    register
     4 - Error   register (?)
  I know these registers are used by the RS-232 routines, but I
  don't know what they really do. Who can help me??

- Is there a 'Programmer's Reference Guide for the Plus4' available
  just like the 'Programmer's Reference Guide for the 64'?

- Where can I get circuit-diagrams of these computers?

I would appreciate it, if someone could help me. If you have information
you can 'e-mail' it to me or post it to me by physical mail.
Thanks for your cooperation.

Gerard Brouwer
P.O.-Box 4117
3102 GC  Schiedam
The Netherlands

E-mail: brouw@dutesta.UUCP