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In some cases different manufacturers use the same Chip Number but provide additional features over their rivals - in these cases all the possible features and the best quoted values will be listed. Also some of the parameters may be mutually exclusive so if it says voltage range 2.7 - 6v and max speed 33Mhz you may be able to get 2.7v parts and you may be able to get 33Mhz parts but you may not be able to get 2.7v parts that run at 33 MHz - you will need to check the datasheet. We judged that listing all possible combinations would involve the risk of going mad before we had finished the first microprocessor family!

Here are details of each heading under which the chips have been classified.

The part number of the chip. We have included similar parts more than once if the part number is different, but only if this is because of different memory types. (e.g. 83C552, 87C552).We have not included preceding manufacturer's letters unless we have found specific differences that can only be identified in this way.

Some chips are supplied with numeric suffixes representing different speed parts, these have been ignored but a speed range is included in the chip data. The actual chip part number will be specific to the speed, memory type, package type and temperature range, so check the data sheet for the exact part number you require.

In the comparative reports the chip number is used as a hyperlink to a separate web page per chip giving the following details for that chip.

Companies which manufacture this chip.

The width of the primary internal registers in bits - this may not be the width of the external data bus.

The amount of program memory that is included on the chip, in bytes. Normally Read Only Non-volatile unless stated.

The type of on-chip ROM/Code Space. This will be one of the following:

• ROMless - no on-chip ROM included on this device
• ROM - Mask programmable ROM
• OTP - One time Programmable ROM
• EPROM - Electrically Programmable Read Only Memory - usually UV erasable
• EPROM(ISP) - Electrically Programmable Read Only Memory - In-situ programmable
• Flash - Multi-write EEPROM (Electrically Erasable Programmable Read Only Memory)
• Flash(OTP) - One-time programmable Flash memory
• Flash(Fact.) - Factory programmed Flash memory
• Flash(ISP) - In-situ programmable
• Flash(ISP+IAP) - In-situ programmable and by the application
• Piggy-back - you can plug an EPROM into a socket on the chip
• NVRAM - an internal or external non volatile RAM that can be loaded with code
• RAM- volatile Random Access Memory that can be loaded with code

The amount of Random Access Memory  that is included on the chip, in bytes which can be used as Stack or Data Space.  Volatile unless stated.

The maximum amount of external memory a device can address. This refers to the sum of program and data memory (if they are different).

8051.....Some chips are designed with enhanced cores that execute instructions using less CPU cycles than the original core. This means the chip has a faster 'equivalent' speed.  For example the original 8051 used 12 clock cycles to execute most instructions hence a core that executed all its instructions in 4 cycles would be 3* faster.  In practice the reduction in cycles cannot usually be applied to all instructions and in the end a 4 cycle machine is rated as having a relative throughput that is 2.5* faster than the clock speed.

ARM.....Some chips have PLLs (phase locked loops) on the chip so that the processor can run at some multiple of the input frequency hence keeping board design and EMI low while running at top speed.  We have taken the maximum MIPS speed given for the chip and used this as it takes account of the efficiency of any cache techniques.

If units such as CAPCOM include additional timers which may be used as simple timer/counters then these will be included in the count of the number of timers.

An onboard watchdog timer, in addition to any standard timers.

This indicates the number of pins on the chip that can be used to trigger an external interrupt against the total number of vectored interrupts available on the device. The total number includes all the interrupt sources on the chip (serial port etc).

RESET is not counted as an interrupt ( yes I've seen designs use it as such but I shudder every time and check that they dont make any medical equipment).

All interrupts are assumed to operate at a single priority level unless specifically stated otherwise in the features section

8051.....Most 8051s have two or more priority levels that the interrupt can be linked to but some small systems have only the one fixed priority at which all the interrupts operate.

ARM.....The original ARM core had very poor interrupt handling capability so most of the manufacturers using it to target embedded applications have provided ISR enhancements on the chip. We have taken the number of IRQs and added one for the FIQ (Fast interrupt request) even if multiple pins can be assigned to the FIQ.

This column indicates the MAXIMUM number of pins that can be used for I/O on the largest pin count package the chip is available in. Bear in mind, however, that many of these pins are multi-function and that use of an External memory bus; any on-board serial port and any ADCs may all use up these pins. Where the chip has no on-board program memory it is assumed that all the I/O pins needed to generate a full external address and data bus are used up.

This column indicates the MAXIMUM number of I/O Lines available if the chip is used with external memory.

The number of UARTS available on the device. These can be UARTs or USARTs, but excluding other serial protocols such as I²C or CAN.

The maximum number of Analogue-to-Digital Converter inputs on the chip, which may be multiplexed into one ADC or each attached to separate converters.

ADC resolution, the maximum number of bits available from an on chip ADC .

The number of separate autonomous Pulse Width Modulated outputs on the device.

The operating voltage range.

The maximum current drawn by the device when it is running or 0 if the data was unavailable. Typical current seems to be approx 50% of max.

The maximum current drawn by the device when it is in idle mode. If this value is zero, then the device does not have an idle mode, or the data was unavailable.

The speed, in MHz, that I-CC and I-ID were measured at. Of course both the clock speed and voltage you use in you design will affect the current drawn.

Indicated that the device appears to be specifically designed for low power operation. This is currently an arbitrary judgment based on it having some sort of idle mode as what might be considered low power for a chip with high functionality would be unacceptable for something with only 2 I/O ports.

The package type the device comes in. The 2 or 3 digit number denotes how many pins are on the device, the letters indicates the style of package as follows:

• DIP - Dual In-line Package
• SDIP - Slim Dual Inline Package
• LCC - Leaded Chip Carrier
• QFP - Quad Flat Pack
• SO - Small Outline
• DSO - Dual Small Outline
• SSOP - Shrink Small Outline Package
• TSSOP - Thin Shrink Small Outline Package
• VSO - Very Small Outline Package
• MLP - Micro Leadframe Package
• PGA - Pin Grid Array
• BGA - Ball Grid Array
• ECP - Encapsulated Package
• SIMM - Single Inline Memory Module

P or C prefixed onto any of the above denotes Plastic or Ceramic respectively.

• C - Commercial (0 to +70 degrees C),
• E - Extended (-40 to +85 degrees C),
• A - Automotive (-40 to +125 degrees C)
• M - Military (-55 to +125 degrees C)

N.B. For automotive devices, current/voltage values vary from the standard - check the data sheet for details.

Indicates clock types supported

• Crystal
• RC
• Ceramic
• External
• LC
• PLL - Phase Locked Loop

These are additional features that the chip has that do not correspond to any of the above categories. Full details of what a specific feature does can be found on the appropriate manufacturers website (see The Embedded Web for links) and/or the device's data sheet. Every effort has been made to stick to the following abbreviations so you can use string searches to identify:

Link(s) to the .pdf file(s) for the device normally on the manufacturers web site. All .pdf files require Adobe Acrobat Reader to view (which is free), and are usually between 200K and 5M in size ( Dallas currently hold that unenviable record). If the link does not take you directly to the .pdf file, it will be no more than two clicks away.

Note

You may not find a chip on the database if:

• The part is not yet sampling
• Sufficient data is not publicly available to make the listing valid
• The CPU is so deeply integrated into a functionality as to make its general use unlikely ( so we will list a chip that has a USB interface, but not one that is clearly designed to control a 4 port USB hub but that gives access to the code space to allow manufacturers to customise it )
• Chips that are known to no longer be manufactured, or are not advised by the manufacturer for new designs, are excluded but not all manufacturers supply this information so don't forget to double check availability with your distributor.

If you have chosen your chip now go to our Tools Directory to find which ICE/Compilers etc are available to help you with its development.