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PICList Thread
'PIC17C42'
1997\10\15@164143 by WF AUTOMA‚̀O

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HI AGAIN!

       I intend to use the PIC17C42 in the Microprocessor Mode, having
8K of EPROM  program and 8K of RAM data and have some doubts:

       -What is the LSB and MSB memory that is described in Databook?

Must i have to care the Even and Odd address?
Must i have 2 EPROM and 2 RAM (for odd and even Address), like the the
8086 microprocessor, or only use the configuration like 8032 Von Neumann
configuration, with a latch for MSB address!

       If someone have a circuit, i will be happy!

       Miguel.

1997\10\15@193752 by Andrew Warren

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WF AUTOMA_AO <spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU> wrote:

> I intend to use the PIC17C42 in the Microprocessor Mode, having 8K
> of EPROM  program and 8K of RAM data and have some doubts:
>
> -What is the LSB and MSB memory that is described in Databook?

   mIGUEL:

   The PIC17C42's program memory is 16 bits wide; the LSB and MSB
   refer to the two 8-bit halves of each 16-bit word.

> Must i have to care the Even and Odd address?
> Must i have 2 EPROM and 2 RAM (for odd and even Address), like the
> the 8086 microprocessor, or only use the configuration like 8032 Von
> Neumann configuration, with a latch for MSB address!

   If you're using 8-bit RAMs and EPROMs, you need two of each in
   order to provide both halves of each program-memory word... It's
   not EXACTLY like the 8086's even/odd addressing, since the 17C42
   treats every pair of bytes as two halves of the SAME address,
   but it's similar.

   The address lines are NOT multiplexed as they are on the 8032.

> If someone have a circuit, i will be happy!

   The 17C4x data book contains a simple diagram for using 8-bit
   memories; if you buy 16-bit memories, your circuit becomes much
   simpler.

   One thing to watch for:  The 17C42 wants to talk to its memory at
   VERY high speeds... You may have some difficulty finding memories
   and latches that can keep up, especially if your address decoding
   logic is complicated.

   -Andy

=== Andrew Warren - .....fastfwdKILLspamspam@spam@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499

1997\10\16@003400 by Mike Keitz

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On Wed, 15 Oct 1997 17:06:39 -0700 WF AUTOMA=?iso-8859-1?Q?=C7=C3O ?=
<wfspamKILLspamAMBIENTE.COM.BR> writes:
>HI AGAIN!
>
>        I intend to use the PIC17C42 in the Microprocessor Mode,
>having
>8K of EPROM  program and 8K of RAM data and have some doubts:
>
>        -What is the LSB and MSB memory that is described in Databook?
>
The program memory must be 16 bits wide.  This means 2 nx8 bit devices.
16-bit EPROMs are available, but not very common.  The LSB and MSB apply
only for the internal to the PIC operation of loading the data in and out
of the data table latch, which must be done 8 bits at a time since the
file registers are 8 bits.

>Must i have to care the Even and Odd address?

No.  There is no signifigance of even and odd addresses.  All addresses
are word addresses, and all reads and writes are 16 bits at a time.
Logic typically used with the 8086 to write low 8 bits, high 8 bits, or
all 16 bits isn't applicable here.  If the software is to write 8 bits at
a time to 16-bit RAM, it must do a TABLRD instruction first to read the
other 8 bits in the word so they won't be changed.

>Must i have 2 EPROM and 2 RAM (for odd and even Address), like the the
>8086 microprocessor, or only use the configuration like 8032 Von
>Neumann
>configuration, with a latch for MSB address!

You can use memory only 8 bits wide (or any width for that matter) for
data-only storage.  The software can ignore the unavailable bits.  But,
any code to be executed must be stored 16 bits wide so the PIC can get
the complete instruction in 1 read cycle.

The external circuit has to latch *all* bits of the address.

>
>        If someone have a circuit, i will be happy!

The circuit is easy to describe, but tedious to wire.  Ports C and D are
the 16-bit multiplexed AD bus.  Connect it to the I/O pins of the memory
chips, and to the inputs of two 74HC373 8-bit latch chips.  Pin 30
(ALE/RE0) to the LE pins of the latches.  Tie the 373's output enable
pins low.  The outputs of the 373's go to the address inputs of the
memory chips.  If you have more than one set of memory chips (e.g. EPROM
and RAM chips), send some of the high addresses to an address decoder
that controls the CE lines so only one pair of chips is enabled at a
time.  If there's only one pair of memory chips it's OK to tie CE on the
chips low (though this will make them draw more power).  OE and WE of the
memories are controlled directly from the PIC pins 29 and 28
respectively.

If you intend to operate the PIC at medium to high speed, check the
timing carefully.  Fast memory chips are required.  If I were faced with
an application that needed so much code or fast data memory that external
chips are required I probably wouldn't use the PIC17.  The 8051 type
chips or the 68HC ones are slower than PIC, but the external memory is
only 8 bits wide so a lot less hardware and wiring is required.

1997\10\16@054203 by Frans Gunawan

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At 05:06 PM 10/15/97 -0700, you wrote:
>HI AGAIN!
>
>        I intend to use the PIC17C42 in the Microprocessor Mode, having
>8K of EPROM  program and 8K of RAM data and have some doubts:
>
>        -What is the LSB and MSB memory that is described in Databook?
because you need 16 data bus(2 EPROM, 2 RAM)

>
>Must i have to care the Even and Odd address?
MPLAB can do this(split hex)

>Must i have 2 EPROM and 2 RAM (for odd and even Address), like the the
>8086 microprocessor, or only use the configuration like 8032 Von Neumann
>configuration, with a latch for MSB address!
the address just same, only data bus

>
>        If someone have a circuit, i will be happy!

yes, just download schematics(in PDF) from my homepage.
goodluck
http://www.poboxes.com/f
f

1997\10\16@183058 by WF AUTOMA‚̀O
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Frans Gunawan wrote:
{Quote hidden}

Frans! Excelent your circuit!

I will try to build your circuit, but my problem is that there is not documented
the LOGIC OF
GAL! I don't know that address that you choose for the I/O!

Miguel.

1997\10\17@142854 by WF AUTOMA‚̀O

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Frans Gunawan wrote:
{Quote hidden}

--

THANK'S!

cOULD YOU GIVE THE DESCRIPTION OF CIRCUIT INTO THE GAL?

mIGUEL.

1997\10\17@185334 by Frans Gunawan

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At 08:29 PM 10/16/97 -0700, you wrote:
>Frans Gunawan wrote:
>I will try to build your circuit, but my problem is that there is not
documented
> the LOGIC OF
>GAL! I don't know that address that you choose for the I/O!

here is the equation for gal16v8:
BA15 BA14 BA13 RD WR BA2 BA1 BA0 NC GND
RESL RESH RAM IOADDRLO IOADDRHI DATAIN DATAOUT NC 259 VCC
@DEFINE IOREG "/(BA15 * BA14 * BA13)"
@UES FGUNAWAN
EQUATIONS

/RAM            = BA15  * /BA14 * /BA13
/DATAIN = /IOREG* /RD
/DATAOUT        = /IOREG* /WR   * /BA2  * BA1   * /BA0
/IOADDRLO       = /IOREG* /WR * /BA2    * /BA1  * /BA0
/IOADDRHI       = /IOREG* /WR * /BA2    * /BA1  * BA0
/259            = /IOREG* /WR * BA2
RESH            = /RESL

goodluck
http://www.poboxes.com/f
f

1997\10\20@091140 by WF AUTOMA‚̀O

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Frans Gunawan wrote:
{Quote hidden}

Thank's!

I will verify this week!

Miguel.


'pic17c42'
1999\06\11@034439 by zelda
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Hello,

   How can i read back my protected pic17c42 ......

1999\06\11@035733 by Eric Smith

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>     How can i read back my protected pic17c42 ......

You're much better off just using the source code.  Screwing with the code
protection is a hassle, and disassembly won't give you the labels and
comments.  The source code is much easier to deal with.

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