HPC167064 datasheet(30/34 Pages) NSC

30 / 34 page

Code Efficiency

One of the most important criteria of a single chip microcon-

troller is code efficiency The more efficient the code the

more features that can be put on a chip The memory size

on a chip is fixed so if code is not efficient features may

have to be sacrificed or the programmer may have to buy a

larger more expensive version of the chip

The HPC family has been designed to be extremely code-

efficient The HPC looks very good in all the standard cod-

ing benchmarks however it is not realistic to rely only on

benchmarks Many large jobs have been programmed onto

the HPC and the code savings over other popular micro-

controllers has been considerable

Reasons for this saving of code include the following

SINGLE BYTE INSTRUCTIONS

The majority of instructions on the HPC167064 are single-

byte There are two especially code-saving instructions JP

is a 1-byte jump True it can only jump within a range of plus

or minus 32 but many loops and decisions are often within

a small range of program memory Most other micros need

2-byte instructions for any short jumps

JSRP is a 1-byte subroutine call The user makes a table of

the 16 most frequently called subroutines and these calls

will only take one byte Most other micros require two and

even three bytes to call a subroutine The user does not

have to decide which subroutine addresses to put into the

table the assembler can give this information

EFFICIENT SUBROUTINE CALLS

The 2-byte JSR instructions can call any subroutine within

plus or minus 1k of program memory

MULTIFUNCTION INSTRUCTIONS FOR DATA MOVE-

MENT AND PROGRAM LOOPING

The HPC167064 has single-byte instructions that perform

multiple tasks For example the XS instruction will do the

following

1 Exchange A and memory pointed to by the B register

2 Increment or decrement the B register

3 Compare the B register to the K register

4 Generate a conditional skip if B has passed K

The value of this multipurpose instruction becomes evident

when looping through sequential areas of memory and exit-

ing when the loop is finished

BIT MANIPULATION INSTRUCTIONS

Any bit of memory IO or registers can be set reset or

tested by the single byte bit instructions The bits can be

addressed directly or indirectly Since all registers and IO

are mapped into the memory it is very easy to manipulate

specific bits to do efficient control

DECIMAL ADD AND SUBTRACT

This instruction is needed to interface with the decimal user

world

It can handle both 16-bit words and 8-bit bytes

The 16-bit capability saves code since many variables can

be stored as one piece of data and the programmer does

not have to break his data into two bytes Many applications

store most data in 4-digit variables The HPC167064 sup-

plies 8-bit byte capability for 2-digit variables and literal vari-

ables

MULTIPLY AND DIVIDE INSTRUCTIONS

The HPC167064 has 16-bit multiply 16-bit by 16-bit divide

and 32-bit by 16-bit divide instructions This saves both

code and time Multiply and divide can use immediate data

or data from memory The ability to multiply and divide by

immediate data saves code since this function is often

needed for scaling base conversion computing indexes of

arrays etc

Development Support

The HPC167064 acts as a stand alone emulator for either

the HPC16083 or the HPC16064 No separate development

tool is thus provided to support this emulator device The

user will use either the HPC16083 or the HPC16064 (de-

pending on which device is in use) development tools to

develop and debug the application hardware and software

in their target as normally done for the non-emulator HPC

devices The application software can then be programmed

in the on-chip EPROM and the HPC167064 can then be

plugged in the target system to run the application like a

regular masked ROM device The HPC167064 can be pro-

grammed using a DATA IO UNISITE with pinsite module

To support the security feature of the HPC167064 a soft-

ware switch is provided with the linker (under PROMHPC)

which will generate an encrypted hex file for the user The

purpose is to be able to compare this software generated

encrypted data with the encrypted data produced by the

actual chip to provide a way to verify on-chip EPROM code

after security has been enabled For details of how to gener-

ate encrypted data and all other HPC167064 features refer

to the Appendix K of the HPC Family User’s Manual

HPC167064 Datasheet(PDF) 30 Page - National Semiconductor (TI)

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