Cheap 8-bit micro with external bus interface?

Dear All,

I'm looking for a cheap 8/16 bit uP/uC that has an external bus interface, 
so that about 256k of SRAM can be addressed. It needs to have on-board 
Flash, around 32k would be good. The device doesn't need many GPIO pins, 
perhaps 5 or so just in case. It doesn't need ADC/DACs, USB etc like all the 
manfs seem to throw in them these days. It will be running a TCP/IP stack 
with link layer to connect to modem, so the processor also needs a UART. 
Price needs to be <$1.50 or so, in 100k quantities.

Any ideas? To recap:

<$1.50 for 100k+
8/16-bit
32k onboard Flash
External bus interface
Handful of GPIO
UART

I would really appreciate it if anyone has any suggestions. I've tried 
Renesas and they can't even come close price-wise.

Very many thanks in anticipation,

Clive Wilson 

Dear All,

On reflection, it needs two UARTs. The rest's the same.

Thanks again,

Clive Wilson

"Clive Wilson" <clive@nowhere.invalid> wrote in message 
news:htmdnSJxXdlTVmXcRVnyvQ@giganews.com...
> Dear All,
>
> I'm looking for a cheap 8/16 bit uP/uC that has an external bus interface, 
> so that about 256k of SRAM can be addressed. It needs to have on-board 
> Flash, around 32k would be good. The device doesn't need many GPIO pins, 
> perhaps 5 or so just in case. It doesn't need ADC/DACs, USB etc like all 
> the manfs seem to throw in them these days. It will be running a TCP/IP 
> stack with link layer to connect to modem, so the processor also needs a 
> UART. Price needs to be <$1.50 or so, in 100k quantities.
>
> Any ideas? To recap:
>
> <$1.50 for 100k+
> 8/16-bit
> 32k onboard Flash
> External bus interface
> Handful of GPIO
> UART
>
> I would really appreciate it if anyone has any suggestions. I've tried 
> Renesas and they can't even come close price-wise.
>
> Very many thanks in anticipation,
>
> Clive Wilson
> 

Clive Wilson wrote:
> Dear All,
> 
> I'm looking for a cheap 8/16 bit uP/uC that has an external bus interface, 
> so that about 256k of SRAM can be addressed. It needs to have on-board 
> Flash, around 32k would be good. The device doesn't need many GPIO pins, 
> perhaps 5 or so just in case. It doesn't need ADC/DACs, USB etc like all the 
> manfs seem to throw in them these days. It will be running a TCP/IP stack 
> with link layer to connect to modem, so the processor also needs a UART. 
> Price needs to be <$1.50 or so, in 100k quantities.
> 
> Any ideas? To recap:

And what's the problem with 32-bit ones? Too easy memory addressing or 
too high processing speed?

Seriously, at that price you could probably dream of not-too-fast '51 
and using external memory above 64K is a nighmare on 8/bit MPUs. Your 
specs can be easily met by almost any ARM and many Renesas H8 chips at a 
slightly higher price. Anyway I don't believe you will get a 
contemporary '51 chip with 2 UARTS at $1.5.

"Grzegorz Mazur" <easy2find@the.net> wrote in message 
news:ctalfl$ja4$1@julia.coi.pw.edu.pl...
> Clive Wilson wrote:
>> Dear All,
>>
>> I'm looking for a cheap 8/16 bit uP/uC that has an external bus 
>> interface, so that about 256k of SRAM can be addressed. It needs to have 
>> on-board Flash, around 32k would be good. The device doesn't need many 
>> GPIO pins, perhaps 5 or so just in case. It doesn't need ADC/DACs, USB 
>> etc like all the manfs seem to throw in them these days. It will be 
>> running a TCP/IP stack with link layer to connect to modem, so the 
>> processor also needs a UART. Price needs to be <$1.50 or so, in 100k 
>> quantities.
>>
>> Any ideas? To recap:
>
> And what's the problem with 32-bit ones? Too easy memory addressing or too 
> high processing speed?
>
> Seriously, at that price you could probably dream of not-too-fast '51 and 
> using external memory above 64K is a nighmare on 8/bit MPUs. Your specs 
> can be easily met by almost any ARM and many Renesas H8 chips at a 
> slightly higher price. Anyway I don't believe you will get a contemporary 
> '51 chip with 2 UARTS at $1.5.

Grzegorz,

Thanks for your reply. Two points I'd like to discuss a little more:

1. You mention that using external memory above 64K is a nighmare on 8 bit 
MPUs. Why is this? As long as the data is treated as 'far' by the C compiler 
(no asm please!), then the compiler will take care of the paging. Admittedly 
it takes processor cycles to achieve this. Is this the angle you were coming 
from, or did you have other reservations?

2. You seem to suggest that I could get a sufficiently-spec'ed ARM for less 
than an H8? Really? Which vendor(s) did you have in mind?

Many thanks again in anticipation,

Clive Wilson 

Clive Wilson wrote:
> "Grzegorz Mazur" <easy2find@the.net> wrote in message 
> news:ctalfl$ja4$1@julia.coi.pw.edu.pl...
> 
>>Clive Wilson wrote:
>>
>>>Dear All,
>>>
>>>I'm looking for a cheap 8/16 bit uP/uC that has an external bus 
>>>interface, so that about 256k of SRAM can be addressed. It needs to have 
>>>on-board Flash, around 32k would be good. The device doesn't need many 
>>>GPIO pins, perhaps 5 or so just in case. It doesn't need ADC/DACs, USB 
>>>etc like all the manfs seem to throw in them these days. It will be 
>>>running a TCP/IP stack with link layer to connect to modem, so the 
>>>processor also needs a UART. Price needs to be <$1.50 or so, in 100k 
>>>quantities.
>>>
>>>Any ideas? To recap:
>>
>>And what's the problem with 32-bit ones? Too easy memory addressing or too 
>>high processing speed?
>>
>>Seriously, at that price you could probably dream of not-too-fast '51 and 
>>using external memory above 64K is a nighmare on 8/bit MPUs. Your specs 
>>can be easily met by almost any ARM and many Renesas H8 chips at a 
>>slightly higher price. Anyway I don't believe you will get a contemporary 
>>'51 chip with 2 UARTS at $1.5.
> 
> 
> Grzegorz,
> 
> Thanks for your reply. Two points I'd like to discuss a little more:
> 
> 1. You mention that using external memory above 64K is a nighmare on 8 bit 
> MPUs. Why is this? As long as the data is treated as 'far' by the C compiler 
> (no asm please!), then the compiler will take care of the paging. Admittedly 
> it takes processor cycles to achieve this. Is this the angle you were coming 
> from, or did you have other reservations?

An 8 bit micro will have only 16 address lines -> maximum addressable
range = 0 to 65535 (0x0 to 0xffff) without page switching or similar
tricks. The paging is a nightmare, regardless whether it's done by
the compiler/linker/run-time combination or the programmer.

> 2. You seem to suggest that I could get a sufficiently-spec'ed ARM for less 
> than an H8? Really? Which vendor(s) did you have in mind?

My vote to an Atmel AT91.

-- 

Tauno Voipio
tauno voipio (at) iki fi

Paging over 64k with a 8 bit processor is a pain in the bum with C,you
can try it with sdcc for free and see how badly it copes.
If it wasnt for the cost issue I would recommend one of the many
extended 32 bit variants of the standard '52.

Clive Wilson wrote:
> Dear All,
>><$1.50 for 100k+
>>8/16-bit
>>32k onboard Flash
>>External bus interface
>>Handful of GPIO
>>UART

Sounds like a vanilla C51: these I have recorded from SST

SST89E52RD2-40-C-NJ $1.20/10K   8KF+8KF  1KR   IAP  SPI  PCA  WDOG  P4
SST89E54RD2-40-C-NJ $1.38/10K  16KF+8KF  1KR   IAP  SPI  PCA  WDOG  P4
SST89E58RD2-40-C-NJ $1.55/10K  32KF+8KF  1KR   IAP  SPI  PCA  WDOG  P4

 >
 > On reflection, it needs two UARTs. The rest's the same.

the above devices have SPI and UART, so might do ?
Or do one UART in SW ?, the PCA can help that.

Two HW uarts tends to move into the 'other extras', so the price
moves up. Look at Winbond's C51's and Dallas's C51's

-jg

Tauno Voipio wrote:

> Clive Wilson wrote:
>> Thanks for your reply. Two points I'd like to discuss a little more:
>>
>> 1. You mention that using external memory above 64K is a nighmare on 8 
>> bit MPUs. Why is this? As long as the data is treated as 'far' by the 
>> C compiler (no asm please!), then the compiler will take care of the 
>> paging. Admittedly it takes processor cycles to achieve this. Is this 
>> the angle you were coming from, or did you have other reservations?
> 
> 
> An 8 bit micro will have only 16 address lines -> maximum addressable
> range = 0 to 65535 (0x0 to 0xffff) without page switching or similar
> tricks. The paging is a nightmare, regardless whether it's done by
> the compiler/linker/run-time combination or the programmer.
> 
>> 2. You seem to suggest that I could get a sufficiently-spec'ed ARM for 
>> less than an H8? Really? Which vendor(s) did you have in mind?
> 
> 
> My vote to an Atmel AT91.

but nowhere near $1.50, esp with external bus...

This is a high volume (100K) app, so 50c = $50K.
This is also DATA, not Code in the 256K.

Thus yes, the access is not invisible, but it is also
not a nightmare. Simply equates to a little more nous, and
engineering time, which saves on the BOM.

-jg

>
> I'm looking for a cheap 8/16 bit uP/uC that has an external bus interface,
> so that about 256k of SRAM can be addressed. It needs to have on-board
> Flash, around 32k would be good. The device doesn't need many GPIO pins,
> perhaps 5 or so just in case. It doesn't need ADC/DACs, USB etc like all
the
> manfs seem to throw in them these days. It will be running a TCP/IP stack
> with link layer to connect to modem, so the processor also needs a UART.
> Price needs to be <$1.50 or so, in 100k quantities.
>
> Any ideas? To recap:
>
> <$1.50 for 100k+
> 8/16-bit
> 32k onboard Flash
> External bus interface
> Handful of GPIO
> UART
>

Some calculation:

256kB ext SRAM
------------------
18 address pins
8 data pins
3 control: /RD,/WR,/CS
4 UART pins RXD*2, TXD*2
5 I/Os
VCC*2,GND*2,XIN,XOUT,RESET
Anything else?
I think you are going to end up with a 64 pin package.
With a mux bus, and an external latch you will fit into a 44 pin package.

I think you get a 16 kB Flash, no external memory at that price, not 32 kB
The ATmega162 is the lowest cost AVR that has a chance to fit.
Since different architectures generate different amount of
code, it is strange that you specify the code size without
a reference to the CPU architecture.

If the ATmega162 doesnt fit, then the ATmega64
is the next obvious choice but will have a problem pricewise

Maybe you could consider instead the AT91R40008?
This is an 32 bit ARM7TDMI with 256 kB of
internal 32 bit zero waitstate SRAM.
Runs at 66 MHZ, providing 60 MIPS at very low power.

You would use the cheapest external 8 bit flash
you could find, and load it into the SRAM at boot
if you need performance/low power or keep it external
if low performance is acceptable. Loading the code into SRAM of course measn
that
you haev less avaialble for data.

It will be more expensive than $1,50 but you do not need to buy the SRAM
since this is on chip.
How much will that cost?




> I would really appreciate it if anyone has any suggestions. I've tried
> Renesas and they can't even come close price-wise.
> Very many thanks in anticipation,
>
> Clive Wilson
>
>

Tauno Voipio wrote:
> 
> An 8 bit micro will have only 16 address lines -> maximum addressable
> range = 0 to 65535 (0x0 to 0xffff) without page switching or similar
> tricks. The paging is a nightmare, regardless whether it's done by
> the compiler/linker/run-time combination or the programmer.
> 

I've missed the start of this, but a lot depends on how the OP wants to 
use the RAM. It's easy enough to set up a paged access scheme for any 
amount of RAM with an external latch for the high-order addresses. Of 
course, there is a performance hit, and the compiler can't deal with it 
directly. But I can't imagine that his app is using that much RAM in the 
  ordinary way anyway, not in an 8 bit system.

Paul Burke