CES 520 - WEEK 2 August 29, 2006

• References
• Rabbit 3000 Data sheet
• Rabbit 3000 User's Manual
• Rabbit 3000 Instruction Manual (microprocessor instruction set)
• Rabbit 3000 Designer's Handbook (information for designers of Rabbit 3000 systems)
• RCM3000 User's Manual (for the "core" module board)
• 3.3V core with 5V tolerant inputs.
• 2 mA/MHz
• EMI reduction
• Separate power supply pins for output buffers prevents CPU core noise getting out the I/O pins
• Clock doubler allows using crystal at 1/2 the frequency
• Clock spectrum spreader
• Claim 15 dB reduction above 100 MHz for FCC class A and B tests
• Phase-modulates the clock signal to "smear out" the emissions spectrum
• Requires 2 to 9 ns faster memory access time
• Causes slight phase jitter on serial clocks
• Low power operation: "Sleepy mode"
• Clock frequency may be divided; divide ratio may be changed under software control.
• Can turn off main oscillator and use real-time clock's 32.768 kHz for super-low power.
• Memory strobes may be shortened in sleepy mode to reduce power.
• Wait-state generation for external memory
• Built-in programming/debug port
• Lots of I/O features
• "Glueless" memory interface to SRAM and Flash devices
• 3 separate CS (chip select) lines for up to 3 memory devices
• 2 each OE (output enable) and WE (write enable) lines
• Optional separate "auxiliary I/O" bus
• Reduces loading on memory bus
• Parallel port A is 8-bit I/O data bus
• Parallel port B provides 6 LSBs of I/O address
• Parallel port E can be configured as I/O CS lines
• Slave port allows multi-processor systems
• The slave may have a slave to daisy-chain more than two processors
• Master may cold-boot the slave and download software via the slave port
• May not use auxiliary I/O bus if slave port is used
• 56 parallel I/O pins
• Shared with serial ports and other features
• Ports D, E, F, G can be configured for timer-synchronized outputs
• Inputs are double-latched to prevent metastability
• 6 serial ports
• Bit rate is system clock rate divided by N, N >= 8
• Clock rate must be selected to be a multiple of serial bit rate
• All may operate asynchronously
• Ports A, B, C, D support SPI synchronous interface
• Ports E, F support HDLC/SDLC synchronous, including IrDA
• Serial port A is used for programming and debug
• Real-time clock (RTC)
• Uses separate 32.768 kHz oscillator
• 3 uA current drain
• Separate power supply pin allows battery backup
• Timers
• Timer A
• Ten 8-bit countown/reload timers
• Peripheral clock = processor clock or procesor clock * 8
• Timer A1 can prescale the others by up to 256
• Timers A2-A7 can be used for:
• Serial port clocks
• Interrupts
• Timer-synchronized parallel output ports
• Timers A8, A9, A10 provide clocks for input capture, PWM, and quadrature decode modules.
• Timer B
• 10-bit counter
• Can be read but not written
• Outputs a pulse on B1 or B2 when the count matches the value in the compare register
• Used for interrupts or timer-synchronization of parallel ports
• Periodic interrupt
• Uses 32,768 kHz oscillator divided by 16
• Interrupt every 488 us, used as general-purpose clock timing
• Watchdog timer (WDT)
• Resets processor if software "gets lost"
• Software must reset WDT before it times out
• Uses 32.768 kHz oscillator
• 17-bit counter allows timeout time of 0.25, 0.5, 1, or 2 seconds
• Potential problem: Be sure WDT can not be reset in an endless loop if software crashes.
• Require several "must execute" sections of code to execute before resetting WDT
• Two "input capture" channels allow time measurements
• 16-bit counter driven by timer A8 (i.e. from clock/256 to full clock rate)
• Measures time difference or absolute time of two events ("start" and "stop")
• Can also be used to synchronize parallel output registers with an input event
• PWM
• 4 PWM channels
• 10-bit resolution (1/1024)
• Implements a 10-bit D/A converter if the output is properly filtered.
• Pulses can be spread into 4 groups spaced 256 apart for easier filtering
• Two quadrature decoders
• 8-bit up/down counter keeps track of number of shaft pulses.
• Generates interrupt whenever the counter over- or under-flows.
• Encoder input is digitally filtered, clocked with the output of timer A10
• The CPU architecture is based on the old Z-80 microprocessor
• 8-bit data bus.
• High performance is not an issue with many embedded systems.
• Registers
• 8 and 16-bit accumulators
• 16-bit index registers (HL, IX, and IY can be used as accumulators or index registers)
• Flag (status) register
• 16-bit program counter with extension register
• 16-bit stack pointer
• Interrupt registers
• Alternate register set
• Originally used in the Z-80 for fast context switching.
• Rabbit adds new instructions to access these registers directly - doubles number of registers.
• Separate address bus for I/O.
• 16-bit I/O addresses. 64 kB I/O address space.
• Memory address space:
• 16-bit logical memory address. 64 kB logical address space.
• 20-bit physical address. 1 MB physical address space.
• Rabbit memory configuration
• Root Memory: everything below 0xE000
• Base (Root) Segment
• Not to be confused with Root Memory
• Typically 24 kbytes
• Normally mapped to Flash
• Contains
• Root Constants
• Root Code
• BIOS
• Interrupt routines
• Short functions that are called frequently
• Any function that modifies XPC (memory management) register
• Data Segment
• Typically 28 kbytes
• Mapped to RAM
• Contains Root Variables, C variables that are not constant
• Can also contain executable code downloaded from flash, for example:
• Flash programming code
• Self-modifying code
• Debugging aids
• Stack Segment
• Usually 4 kbytes
• Mapped to RAM
• Contains C function automatic variables, that are held on temporary stacks
• Different stacks can be placed in different physical memory pages if more than 4k is needed
• Extended memory: above 0xE000
• 8 kbytes
• Different pages can be mapped to Flash (code or constants) or RAM (buffers)
• For large programs, most program code is in Extended Memory
• Can also be used for variables and buffers to save memory in the Data Segment
• MMU (Memory Management Unit)
• Converts logical addresses to physical addresses
• Automatically shifts the 8-kbyte extended memory segment by 4 kbytes at a time as code executes
• Optional separate Instruction/Data space mode
• Allows using entire Base and Data Segments for both instructions and data
• MMU inverts address lines 16, 19, or both to switch between instructions and data
• By default, Dynamic C compiles with this feature disabled
• Prioritized interrupts
• 3 priority levels
• Up to 4 nested interrupts supported in hardware
• Max. interrupt response time < ~20 clock cycles for highest-priority
• 2 external interrupt lines
• ICP (In-Circuit Programming)
• Flash memory can be loaded unprogrammed.
• Plugging in the programming cable pulls the startup pins (SMODE0, SMODE1) high
• Causes Rabbit to enter cold-boot mode upon reset
• To load new software, Dynamic C
• Forces reset
• Loads and runs a boot program
• Compiles and loads the BIOS and user software
• Runs the BIOS
• Runs and debugs the user program

Other Embedded Microcontroller features

• On-chip memory
• RAM, ROM, or Flash memory for program
• RAM memory for data
• EEPROM memory for non-volatile data
• Code protection - prevents reading of internal program memory
• External memory interface
• Memory-mapped vs port I/O
• Big endian vs little endian
• DMA (Direct Memory Access)
• Transfers data to/from memory automatically, in the background, with minimal software overhead.
• In microcontrollers it is often used to transfer data to/from internal peripherials (e.g. serial ports).
• On-chip voltage regulator (e.g. for 2.5V core with 3.3V supply)
• Brown-out detector (BOD)
• More powerful timers. e.g. PIC:
• Up to one 16-bit and four 32-bit or dual-16-bit timers
• Selectable prescaler
• 32-bit or two 16-bit timers per module
• Timer or counter mode
• Timer gate operation
• Operates during idle and sleep modes
• Counter match register
• Timing for other functions (ADC, input capture, output compare)
• More powerful pulse-width modulator (PWM) e.g. PIC:
• Separate pins for bridge driver
• Up to 16-bit resolution
• Multiple operating modes
• Power-saving features
• Sleep mode
• Turns off nearly all circuitry, including clock(s)
• Exit sleep mode on:
• External interrupt
• Reset
• Watchdog timer timeout
• "Doze" mode
• CPU clock rate is reduced
• System clock and all peripherals continue to operate at full speed.
• Peripheral module disable
• Selectively turn off unused peripherals
• More than 2 external interrupts, more than 3 interrupt priority levels
• Hardware support for various serial interfaces
• SPI
• I²C
• Microwire
• UART (RS-232, RS-485)
• IrDA
• USB
• CAN
• JTAG test port
• Boundary scan testing
• May also be used for in-circuit programming
• Analog interfaces:
• A/D converters
• Typically includes an analog MUX to allow reading multiple voltages with one A/D
• PIC has automatic scan mode with output buffer
• D/A converters
• Often PWM port is used for this purpose
• Analog comparators
• DSP capability
• Typically Harvard architecture: separate program and data address spaces
• Sometimes two separate data spaces as well
• Multiplier/accumulator (MAC)
• Typically can read two values from memory, multiply, and accumulate in one cycle (pipelined)
• Barrel shifter

Choice of microcontroller

• Support for needed I/O interfaces
• Sufficient memory
• Memory architecture
• Number of interrupts
• Processing speed
• ICP and/or ROM version available for high-volume applications
• Processor cost
• Effect on total system cost
• Support for high-level language(s)
• Operating system availability (some real-time operating systems come with C source code)
• Short-term and long-term part availability
• Current knowledge base (is the development team already familiar with the part family)
• Flexibility for use in future projects
• Cost of development tools
• Technical support
• Development tool availability and quality
• IDE (Integrated Development Environment)
• Editor
• Assembler and compiler
• Debugger
• PROM programmer
• ICE (In-Circuit Emulators)
• Development kits

Other manufacturers of embedded microcontrollers

• Microchip PIC
• Low-cost, relatively low-performance parts
• Low-cost, easy-to-use development tools
• Tons of documentation
• Popular with hobbyists
• Lots of peripherals
• dsPIC parts include DSP engine in addition to microcontroller CPU core
• The original 35-instruction architecture parts are awkward to program
• Atmel
• 8051, AT91, and AVR microcontrollers
• Low-cost development tools
• Many parts are targeted to automotive industry
• Rabbit 3000
• Medium-complexity systems
• Closely-integrated development software and tools for rapid prototyping
• Dallas Semiconductor (now a division of Maxim)
• Flash-based 8051 and MAXQ RISC microcontrollers
• Many peripheral chips
• Freescale (former Motorola)
• Wide range of microcontrollers, from 8 to 32 bit, including PowerPC
• Many other semiconductor products
• Infineon (Formerly Siemens)
• 8 to 32-bit microcontrollers
• Intel
• 8 to 32-bit microcontrollers
• 386EX: many development tools available for x86
• National
• COP8
• Renesas (formerly Hitachi)
• Broad-range semiconductor manufacturer, including many microcontrollers
• Analog Devices
• DSPs
• Analog devices, such as the "MicroConverter", a 12-bit ADC with embedded CPU
• Texas Instruments
• Leader in DSPs

Assignments:

• Read An Embedded Software Primer, Chapter 9
• Read Embedded Systems Design, Chapter 2 pp 36-64 and Chapter 3
• Study the Rabbit 3000 Data Sheet
• Look over the Rabbit 3000 User Manual