Looking for 68HC705C8A Replacement In HC908 Family

[MIDIprotocol]

First off, to whomever comments and helps steer my search, thank you for your time.

As my subject topic describes, I am looking for a current production replacement for the 68HC705C8A and here are more specifics that are steering the criteria.  Due to the nature of our first rework phase, we need to retain the following lines and need the following pins functions directly accessible. 

Here is a jpg file of what I am seeking to achieve.

The link below is from our schematic. 
http://www.benderguitars.com/images/gallery/68update/68pinout.jpg

Package SDIP - 40 / 42 pins. 
SCK, MOSI, and MISO. 
We also need non-multiplexed ports, PA, PB, and PC.

The MC68HC908AP8 is very close except that MOSI/MISO is defined with pins on port C.

The closer to the above criteria we can come, the less redesign of our external components and rewriting code. 

The SDIP requirement is related to the ease with which a 40 PDIP can be replaced using our on-board ZIF socket.  All this stated another way would be a current model with all the exact pin function and definitions exacly the same.  If a good match is available in a higher pin count, we will go with a different package. 


Thanks much,

Bill

[PeterHouse]

Have you thought about using a surface mount part and making a drop in module which wil plug into your existing ZIF socket?  You could use a 3.3v part and have the regulator and any extra latches on it.

[bigmac]

Hello Bill,

As you are aware, the 705C8A device contained only a few peripherals, and these had dedicated pins at the expense of a partial Port D.  However, the more recent devices have many more peripherals that require to be multiplexed with GPIO pins.

For the more recent devices, you will find that most of the GPIO ports are only partially implemented, unless you use the highest pin count version (i.e. 64 pins).  Then there is the additional problem that a needed peripheral will consume part of an otherwise complete port, as you have found.

I assume that you would prefer having complete GPIO ports in order to provide parallel byte access to an external peripheral, for example an external parallel RAM device.  If so, I think you will have port allocation problems and may need to modify the approach, at the expense of more substantial changes to the existing code.

For the 705C8A, I presume you were using assembly code.  If so, when migrating to a later device you will probably find it beneficial for the code to make much more use of the stack for temporary storage purposes, an option that was not available for the earlier MCU.

Regards,

Mac

[peg]

Hi Bill,

Take a look at the MC9S08GT16A.
It is available in 42SDIP.
I have migrated a product from HC705C8A to HC08GP32 to S08GT16 to S08GT16A with remarkably minimal effort at each stage. Of course jumping from one end of the path to the other will be harder but still doable. The GT16A is quite new and likely to be around for a long time. 3 full ports plus the SPI is a problem but I'm sure a little coding can fix that. As the GT is a cutdown GB some of the ports are only partially implemented.
I think it may be the closest you will get.

[Ake]

Hi,

If you look at the 9S08 family, there is no SDIP members, so the HC908 is a better choise.

I looked thru the standard HC908, and I agree with you, it seems that the HC908AP8 is the best choise.

Regards,

Ake