Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!pyramid!voder!apple!han
From: han@apple.UUCP (Byron Han, fire fighter)
Newsgroups: comp.sys.mac
Subject: Re: Serial Drivers (RAM and ROM)
Message-ID: <7324@apple.UUCP>
Date: 4 Feb 88 19:04:59 GMT
References: <7312@apple.UUCP> <6500012@hpindda.HP.COM>
Reply-To: han@apple.UUCP (Byron Han, fire fighter)
Organization: Communication Tools Group - Apple Computer, Inc.
Lines: 44

article <6500012@hpindda.HP.COM> atchison@hpindda.HP.COM (Lee Atchison) writes:
>Question:
>Why would anyone want to use the ROM serial driver over the RAM serial driver?

There really is no reason to use the ROM driver.  Originally, space was
tight on the 128K Macintoshes and every byte counted.  These days, space
is not so critical. 

>Where is the RAM serial driver located?  In the System file?

either in the System or in the ROM.  I don't know.  It shouldn't matter.

>Is the RAM serial driver included with all Systems?
>
>I'm writing a program that needs to read and write to the serial port.  I want
>it to work on a variety of different macs.  Is it wrong for me to assume that
>the RAM serial driver will always exist on a system?

References  - Inside Macintosh Volume II, IV

For the Macintosh 128, 512, XL:
    there is a version of the RAM based serial driver in resource SERD, id 1
        for the 128/512, id 2 for the XL

For the Macintosh 512e, Plus, SE, II:
    there is a single new serial driver that replaces the old RAM/ROM serial
        drivers.  "For best results, include the RAM serial drivers as 
        resources of type 'SERD' in the resource fork of your application
        and continue to use RAMSDOpen and RAMSClose.  If the 128K ROM
        (or later) is present, the new driver is automatically included.

Sooooo, if the target machine is 128K ROM or later (see technote 129 to
find out how to determine this), you can assume that using RAMSDOpen and
RAMSDClose will work.  If the target machine is 128/512/XL, then including
the SERD resources will guarantee that RAMSDOpen/RAMSDClose will work.

PLEASE try to use the RAMSDOpen/RAMSDClose calls.  
ALSO ALWAYS ALWAYS ALWAYS call RAMSClose when terminating.  

Cleanliness is always appreciated by the Apple Thought Police :-)
-- 
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