NEC D75008 MCU

[Brent Hilpert]

On 2010 Sep 7, at 9:29 AM, maurice smulders wrote:

> I think I have the NEC databook containing the series. Do you need a 
> scan?

Thanks, but no, I'm not planning on doing anything with the MCU (the 
photocopier was being discarded and the MCU is internally programmed).
I was just interested in knowing something of the architectural/family 
provenance of the MCU as I had never run across it before.


> On Mon, Sep 6, 2010 at 5:13 PM, allison <ajp166 at verizon.net> wrote:
>> On 09/06/2010 02:34 PM, Brent Hilpert wrote:
>>>
>>> On 2010 Sep 6, at 5:56 AM, allison wrote:
>>>
>>>> On 09/05/2010 10:06 PM, Brent Hilpert wrote:
>>>>>
>>>>> I just ran across an NEC D75008 microcontroller in a small photo 
>>>>> copier
>>>>> ca. 1990. According to a search it is a 4-bit microcontroller.
>>>>>
>>>>> Idle curiousity, but does anybody know if this has any inheritance 
>>>>> from
>>>>> or relation to better-known microcontrollers such as the TMS1000, 
>>>>> that is,
>>>>> is it NEC's version of something better known?, or is it NEC's own
>>>>> architecture?
>>>
>>>> No,  it is NEC unique.  For 4 bitters that is usually the case.   
>>>> it is a
>>>> much more expanded
>>>> design closer to modern PICs with many variants having LCD driver on
>>>> board.
>>>
>>> OK, a family I had never run across before. Found a datasheet for (by
>>> appearance) a descendant (D75112/6). Looks like they took a cue from 
>>> the
>>> 8080 family - the register set is nearly identical but in 4 bits, 
>>> with
>>> register pairs BC, DE, HL to make 8-bit registers.
>>>
>>
>> Many of the 4bit MCUs did that.  The instruction set is is similar to 
>> 8080
>> and different since it has
>> skip on condition and typical Harvard oddities and additions for 
>> tables and
>> inline constants.
>>
>> The family closest to it is the 1980s ucom75.