Midsize Microcontrollers and Microprocessors

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Midsize Microcontrollers and Microprocessors

• The 8051 is an example of a small inexpensive
  microcontroller intended for simple applications.
• Other examples are the PIC and the Atmel AVR.
• There are also a large number of more powerful
  midsize microcontrollers available.
• These include embedded X86 processors.
• These typically provide more memory, more I/O and
  faster performance.
• We will consider an interesting example, the
  Rabbit 3000 developed by Z-world.
• The Rabbit processors are enhancements of the Z80
  processor.

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The 3200 Core module

• Rabbit Semiconductor sells the 3000 as a module.
• For modest volume applications using this module
  is more viable than building a system form
  scratch.

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Rabbit 3000 Processor

• 8-bit data bus
• 20-bit address bus
• Internal peripherals use 8 bit address bus
• Static design - DC to 54 MHz Clock
• Programmable chip select outputs
• Clock Spreader results in Ultra-Low EMI
• Communication FeaturesHardware and/or software
  support for TCP/IP, IrDA, SDLC/HDLC, Async, SPI,
  I2C
• 56 Digital I/O
• 6 Serial Ports
• 1.8-3.6 V (5 V tolerant I/O)
• Watchdog Timer
• Extended Low-Power "Sleepy" ModesDynamic,
  software-enabled low-power modes

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Processor Registers

• Multiple Accumulators
• A 8 Bit
• HL 16 Bit
• Memory Mapping
• IX,IY Index Registers
• XPC Extension of PC
• Two Register Banks
• A, F, HL, DE, BC all have alternate registers.
• EX AF, AF swaps AF and AF
• EXX swaps HL, DE, and BC with HL, DE, and
  BC.

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Parallel I/O ports

• Seven 8-bit I/O ports. (A-F)
• I/O pins are shared with other on-chip
  peripherals.

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Other ports

• Six Serial Ports
• Maximum baud rate of system clock divided by 8
• Several enhancements over standard asynchronous
  communications.
• The serial ports can be used for processor to
  processor communication.
• A parallel slave ports are also provided for
  processor to processor communication.

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Slave port example
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Quadrature Decoder

• Two channels for encoder input (IQ)
• 8-bit counter is incremented or decremented to
  keep track of encoders position.

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Pulse width modulation (PWM) channels.

• PWM is useful in many applications from audio
  generation to motor control.
• Four independent channels are provided.
• The Rabbit PWM module is straightforwarda single
  10-bit free-running counter counts from 0x000 to
  0x3FF (0 to 1023) and rolls over. The application
  program loads a PWM width register with a value
  n. Out of 1024 counts, the PWMs output pulse
  is high for n1 counts. This gives the
  application the ability to vary the duty cycle
  from about 0.1 to 100. 1024 ticks from timer A9
  define the overall period.

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Timers two timer modules A and B
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Memory - MMU and MIU

• MMU memory management unit
• MIU memory interface unit
• Combination allow for addressing 6 MB
• 20-bit physical address for 1 MB
• Internally 16 bit address are used (64 KB)
• MMU uses special segment registers to map 16 bit
  address to 20 bit address.

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• Base (or Root) Segment 0000 ? 00000
• Data Segment X000 ? DATASEG000
  X000
• Stack Segment Y000 ? STACKSEG000
  Y000
• Extended Memory Segment E000 ? XPC000 E000

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Memory Mapping Example
Base (or Root) Segment 0000 ? 00000 Data Segment
X000 ? DATASEG000 X000 Stack
Segment Y000 ? STACKSEG000
Y000 Extended Memory Segment E000 ? XPC000 E000

• Example
• The MMU registers are set as follows
• XPC        0x85
• SEGSIZE    0xD7
• STACKSEG   0x80
• DATASEG    0x79
• The physical address of the bottom of the xmem
  segment is given by
• 0x85000 0x0E000 0x93000
• The physical address of the bottom of the stack
  segment is given by
• 0x80000 0x0D00 0x8D000
• The physical address of the bottom of the data
  segment is given by
• 0x79000 0x07000 0x80000

Y X
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MIU