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Frequently asked questions
LPC2000 Family ARM7TDMI-S Core FAQ
- Can you recommend a good book on ARM architecture?
- Does LPC2000 have good multiply or multiply-and-accumulate (MAC) functions?
- Having the Thumb core allows more compact code and better performance. Are there any trade offs?
- Can spurious interrupts occur in the LPC2000?
- Where can I find LPC2000 family instruction set details?
- Where can I found more information on interrupt handling?
- Is the ARM system mode ever needed in a typical ARM application?
- While initializing the LPC2000 ARM7 core, what things do I need to take into consideration?
- What is the maximum operating speed for LPC2000 devices?
| Q | Can you recommend a good book on ARM architecture? |
| A |
ARM - System on Chip Architecture by Steve Furber (Addison Wesley ISBN 0-202-67519-6) The Insiders Guide to the NXP ARM®7 Based Microcontrollers by Hitex Development Tools |
| Q | Does LPC2000 have good multiply or multiply-and-accumulate (MAC) functions? |
| A | The ARM7TDMI-S core we use has excellent Multiply and Multiply-Accumulate capability and can be run at 75MHz (LPC2220) offering good DSP capability. |
| Q | Having the Thumb core allows more compact code and better performance. Are there any trade offs? |
| A | Thumb is a 16-bit compressed instruction set that is decoded by the Thumb core into full 32-bit instructions that are then fed into an ARM core for execution. Thumb increases code density drastically. The trade offs are that the Thumb instruction set loses the conditional instruction capability and can only address the first eight registers of the processor. |
| Q | Can spurious interrupts occur in the LPC2000? |
| A |
Spurious interrupts can occur in all devices of the LPC2000 family except the LPC23xx and LPC24xx series.
The following application note covers this topic in detail:
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| Q | Where can I find LPC2000 family instruction set details? |
| A |
The LPC2000 has a licensed ARM7 core, and the instruction set information can be found on the ARM website.
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| Q | Where can I found more information on interrupt handling? |
| A |
Three application notes are available online that deal with interrupt handling in detail:
For more information, please refer to the ARM7TDMI-S Technical Reference Manual which can be downloaded from the ARM website.
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| Q | Is the ARM system mode ever needed in a typical ARM application? |
| A |
Yes.
Nesting of interrupts in an ARM application involves system mode.
Application note AN10381 shows how nesting of interrupts can be effectively handled using system mode.
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| Q | While initializing the LPC2000 ARM7 core, what things do I need to take into consideration? |
| A |
Initialization of the ARM7 core has to be done in the ARM startup assembly code.
This would typically include setting the interrupt vectors and initializing the stack for the various ARM operating modes.
In the C code, typically the LPC2000 device needs to be initialized.
Application note AN10404 shows how this can be done:
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| Q | What is the maximum operating speed for LPC2000 devices? |
| A |
Many of the LPC2000 devices can operate up to 72MHz.
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Other Questions
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