June 11th, 2015 ~ by admin

Dallas: Reaffirming the Viability of the 8-bit Processor

The introduction of the Dallas Semiconductor DS87C520 reaffirms the viability of 8-bit processors for new and demanding applications.  Those were the words written about the the Dallas DS87C520 (and its ROMLess version the DS80C320) in 1994. The Intel MCS-51 architecture it was based on had been released 13 years prior, in 1981 and ran at up to 12MHz.  By 1994 the Pentium had been released, with speeds of up to 100MHz.  Full 64-bit processors were also available, yet the 8-bit processor continued to hold on, and grow.

Dallas Semi. was founded in 1984, by former Mostek employees.  Their first products were lithium battery backed SRAMs, a product pioneered by Mostek.  Dallas added power saving and sensing circuitry to them though, greatly enhancing their usefulness.  In 1987 they combined with with an MCS-51 microcontroller to make the DS5000, which ran at 16MHz and provided battery backed SRAM.

With the release of the DS87C520 in 1994 they redesigned the MCS-51 core, allowing it to complete a machine cycle in 4-clocks vs the original 12.  They were plugin compatible, providing a simple speed up for 8051 systems.  Max clock was also raised, to 33MHz as well as additional interrupts, 16K of EPROM, an extra 1KB of SRAM and many power saving features/modes.  Other companies (such at Philips, and Atmel) began to also make enhanced 8051s, including things such as Flash memory and expanded instructions/features.

Its now 2015, and the 87C520 continues to be made, as does hundreds of other MCS-51.  It was surprising in 1994 that the 8-bit processor continued to be viable, and perhaps to some, even more so, that 21 years later, it is still viable, and shows no signs of slowing down.  The recent push into the Internet-of-Things (IoT) market has 8-bit MCUs in Internet of Things yet again.  While many companies have marked numerous 16-bit and 32-bit designs as ‘a migration path from 8-bit’, that migration is yet to be seen.  There simply is no reason, no need, and no desire to plug a 32-bit processor in where an 8-bit processor, implemented in a few thousand transistors, will do nicely.


March 6th, 2011 ~ by admin

CPU of the Day: NS87P50R-6: Piggyback CPUs

National Semiconductor NS87P50D-11

National Semiconductor NS87P50R-6

In the 1980’s most high-volume microcontrollers were OTP (one-time-programmable) or were factory programmed (Mask ROM).  This made developing code for them a bit tricky.  Some companies made lower volume version with an onboard EPROM, such as the Intel 8751.  Other designs this was not practical so another solution had to be found.

The most common solution became the ‘piggyback’ package.  The CPU would reside on a ceramic (pictured on the left) or organic (on the right) package that had a socket on top of it for an EPROM.  This provided an easy way to develop code for the processor, and EPROMs could be stopped out and erased at will.  Obviously these ‘piggyback’ parts were not intended for production use, their cost would be much to high for that.  They were made in relatively small quantities solely for engineering and prototype work.

This National Semiconductor NS87P50R-6 is a 6MHz MCU.  It includes a 24-pin socket on top that supports up to a 32k EPROM (2758, 2716 or 2732).  The other group of 4 pins on top are yet another feature.  It would be cost prohibitive to make a separate development device for each member of the MCU family so the 87P50 can be told to emulate several.  It can emulate a 8048, 8049, or if all jumpers are removed, the 8050. (The only difference in these is the RAM size, 64bytes, 128bytes, or 256bytes for the 8050).  The NS87P50R-6 is in an organic package, the die is actually placed directly on a circuit board, and covered in a black epoxy.  This is rather less expensive then the NS87P50D-11 ceramic and gold version, though is not as tolerant to heat.

If you have ever taken apart a cheap consumer electronic device, you will likely find a black ‘blob’ on the circuit board.  Thats a die, and usually the microcontroller of that device.  ID’ing it is next to impossible without acid and a microscope however.

National Semiconductor was not the only company to use this type of design.  Zilog and Synertek used it for the Z8 series, Hitachi for the HD6301, Mostek for the 3870 and most all other companies that made a MCU int he 1980’s.

February 14th, 2009 ~ by admin

Processor of the day: COP8 – Now in Gold

National Semiconductors COP8 family of microcontrollers has been around for many years now, and with over a billion shipped, in thousands of configurations, will be around for quite some time.



This is a rather unusual COP8 used for development purposes. This is the first SOIC I have seen in ceramic, let alone with the UV Window.


Posted in:
CPU of the Day

January 13th, 2009 ~ by admin

Dual core CPU…For $1?

When you think of multi-core CPU’s what comes to mind? Intel? AMD? Perhaps Nvidia, but certainly not TI.

Alas though, the embedded CPU/MCU market is by far the largest user of multicore CPU’s.  Many systems controllers have an ARM main core, and then a MCS-51 core for IO stuff, or another ARM core.  The iPhone has no less then 3 ARM cores in it.

TI just released the MSP430FE42X2, in large quantities its a mere $1 US. It includes 2 complete MSP430 cores, along with an LCD driver, and 32K of Flash.  Where will you find it? Its marketed as a complete power meter solution, only other component needed to measure your houses power draw is a voltage regulator.


MSP430 Power Meter

MSP430 Power Meter

The future of embedded computing IS multi-core controllers/ASICs

Source:  TI (Texas Instruments)

Posted in:
Processor News