Chapter 14 Embedded Software development Process and Tools
Lesson-6: Issues in Hardware and Software Design and Co-Design
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 1 Design", Raj Kamal, Publs.: McGraw-Hill Education 1. Choice of Right Platform
Processor Less System
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 2 Design", Raj Kamal, Publs.: McGraw-Hill Education System Platform PLC (Programmable logic unit) instead of Processor
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 3 Design", Raj Kamal, Publs.: McGraw-Hill Education System Platform
Processor Based System
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 4 Design", Raj Kamal, Publs.: McGraw-Hill Education Microprocessor or Microcontroller or DSP based system
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 5 Design", Raj Kamal, Publs.: McGraw-Hill Education System Platform
IP or FPGA Based System
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 6 Design", Raj Kamal, Publs.: McGraw-Hill Education IP and FPGA based system
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 7 Design", Raj Kamal, Publs.: McGraw-Hill Education 2. Software-Hardware Tradeoff
1) Certain subsystems in hardware (microcontroller), real-time clock, system clock, pulse width modulation, timer and serial communication can also be implementable by software.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 8 Design", Raj Kamal, Publs.: McGraw-Hill Education Software-Hardware Tradeoff …
2) Hardware implementations though increase the operation speed but may increase power requirements.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 9 Design", Raj Kamal, Publs.: McGraw-Hill Education Software-Hardware Tradeoff …
3) A serial communication, real-time clock and timers featuring microcontroller may cost more than the microprocessor with external memory and a software implementation
4) Simple coding for device drivers
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 10 Design", Raj Kamal, Publs.: McGraw-Hill Education Software implementation advantages
(i) Easier to change when new hardware versions become available (ii) Programmability for complex operations (iii) Faster development time (iv) Modularity and portability
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 11 Design", Raj Kamal, Publs.: McGraw-Hill Education Software implementation advantages … (v) Use of standard software engineering, modeling and RTOS tools. (vi) Faster speed of operation of complex functions with high-speed microprocessors. (vii) Less cost for simple systems
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 12 Design", Raj Kamal, Publs.: McGraw-Hill Education 3. Performance Accelerators
1) Conversion of CDFGs into DFGs for example by using loop flattening (loops are converted to straight program flows) and using look-up tables instead of control condition tests to decide a program flow path
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 13 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
2) Reusing the used arrays in memory, appropriate variable selection, appropriate memory allocation and de-allocation strategy
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 14 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
3) Using stacks as data structure when feasible in-place of queue and using queue in place of list, whenever feasible.
4) Computing slowest cycle first and examining the possibilities of its speed-up.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 15 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
5) Code such that more words are fetched from ROM as a byte than the multi-byte words
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 16 Design", Raj Kamal, Publs.: McGraw-Hill Education 4. Hardware implementation advantages (i) Reduced memory for the program (ii) Reduced number of chips but at an increased cost (iv) Internally embedded codes, more secure than at the external ROM.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 17 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
- An accelerator may include bus interface unit, DMA, read and write units, registers and accelerator cores. - An accelerator uses a programming model to accelerate, unlike the coprocessor, which has instruction sets for specific tasks.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 18 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
- A processor registers interact and connect to an accelerator through buses so that processor controls the accelerator for obtaining a higher performance.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 19 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
- Example - JA108 from Nazonin Communications, a Java accelerator, which accelerates the JAVA code run by 15 to 60 times. - Another example is a video accelerator, which accelerates video processing tasks.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 20 Design", Raj Kamal, Publs.: McGraw-Hill Education Performance Accelerators …
Hardware accelerator accelerates code execution. It may be an ASIC, IP core or FPGA.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 21 Design", Raj Kamal, Publs.: McGraw-Hill Education 5. Porting IO Instructions issues of in an Embedded Platform
Data type may be different on the different platforms, as follows:
(i) unsigned char* (PowerPC, M68HC11/12, M68K, S390),
(ii) unsigned int (ARM)
(iii) unsigned long (Itanium, Alfa, SPARC)
(iv) unsigned short (80x86)
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 22 Design", Raj Kamal, Publs.: McGraw-Hill Education Interrupt Vectors OS support
Interrupt vectors are to be defined differently
OS supports these differently on different platforms
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 23 Design", Raj Kamal, Publs.: McGraw-Hill Education 6. Interface Addressing Issues
For example, a network interface card supports 32-bit unsigned integers and with a big endian.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 24 Design", Raj Kamal, Publs.: McGraw-Hill Education 7. Data Alignment
(i) Two or three bytes stored at an address from which processor accesses 4-bytes in an access.
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 25 Design", Raj Kamal, Publs.: McGraw-Hill Education Data Alignment…
(ii) Same data structure at ‘C’ source file may show differently on different platforms. [‘C’ takes 16-bit integer on a 16-bit processor and 32-bit integer on a 32-bit processor].
Compiler must force the alignment of data by the OS-hardware interface function
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 26 Design", Raj Kamal, Publs.: McGraw-Hill Education Summary
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 27 Design", Raj Kamal, Publs.: McGraw-Hill Education (i) Choice of Platforms (ii) Software-Hardware Tradeoff (iii) Software methods and hardware Performance accelerators to improve the performance (iv) Porting Issues
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 28 Design", Raj Kamal, Publs.: McGraw-Hill Education We learnt - Data Type and Data Alignment Issues
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 29 Design", Raj Kamal, Publs.: McGraw-Hill Education End of Lesson-6 of Chapter 14 on “Issues in Hardware and Software Design and Co-Design”
Chapter-14 L6: "Embedded Systems - Architecture, Programming and 2015 30 Design", Raj Kamal, Publs.: McGraw-Hill Education