BUS_PORT aka memory mapped I/O $B5xx for MC68HC11 |

OK, I would like to (also) try to use the MC68HC11E9 bus expansion 
port with the already mapped memory ($B5xx), but I can barely find any 
data on it.  My question is, when I call my CS' by writing to the 
appropriate address block, do I first need to set the data pins' (D0-
7) direction?  And if so, how?...should I be wiring up my R/W pin?  Or 
can I just read one address in my CS' block and then turn around and 
write to another address for the same CS'?  TJ

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    OK I am my own answer.....for anyone who's using the BUS_Port of 
the CME11E9-EVBU.  As the SMALL bit of documentation on this port 
says, it is for attaching off-board devices to the E9 that can then be 
read/written through the appropriate "peripheral area" mapped memory 
locations ($B580-$B5FF).  There are 9 CS', including the one for the 
LCD port, in the periphereal area memory.  Each CS' has 16 addresses 
(0-F) associated with it (except for the LCD & CS7' which split the 16 
addresses between them).  So, as long as your external device has 16 
or less internal registers/addresses, you can assign it to any one CS' 
and read/write your external device registers by simply writing to the 
appropriate memory address for that CS'.
    Just storing data to address $B581, for example, automatically 
causes the BUS_Port to send the corresponding address through the A0-4 
(address lines I'm using--14 address lines are actually available), 
fire the CS', and then the WR' and send the data on D0-7 lines.  It 
almost seems like cheating to be able to do all of those operations 
with one simple STAA command!  Likewise, reading from one of the 
mapped addresses causes the BUS_Port to automatically send the 
corresponding address through the A0-4 lines, fire the CS', and then 
the OE' and receive the data on the D0-7 lines.
    I still have no data on the actual timing of the CS'/OE'/WR' 
strobes, but I can say they are compatible with my off-board TTL chip, 
because I am successfully reading and writing it using this 
port....or, as my ex-lab instructor was saying about interfacing my 
TTL device with this port "It's a device.  Of course it's going to 
work.  They set it up so any idiot--I mean user--can use it."  He was 
so right.

--- In m68HC11@m68H..., "teejsd" <tmjorenby@...> wrote:
>
> OK, I would like to (also) try to use the MC68HC11E9 bus expansion 
> port with the already mapped memory ($B5xx), but I can barely find 
any 
> data on it.  My question is, when I call my CS' by writing to the 
> appropriate address block, do I first need to set the data pins' (D0-
> 7) direction?  And if so, how?...should I be wiring up my R/W pin?  
Or 
> can I just read one address in my CS' block and then turn around and 
> write to another address for the same CS'?  TJ
>

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Discussion Groups | | BUS_PORT aka memory mapped I/O $B5xx for MC68HC11

BUS_PORT aka memory mapped I/O $B5xx for MC68HC11 - teejsd - Feb 23 3:12:00 2006

Re: BUS_PORT aka memory mapped I/O $B5xx for MC68HC11 - teejsd - Mar 12 23:15:00 2006