CSE466 Autumn ‘00 Review  Card Key Access…See Kathleen Goforth  Mail Archive…working on it…are you getting my messeges?  Why do we connect the speaker to 5V instead of ground?  Frequency range … what did you discover?  Debugger – shows you elapsed simulation time, can set watch variables, etc, etc. Learn more about the debugger!

CSE466 Autumn ‘00 Simple Princeton Architecture ALU ROM Linear Address Space W/ Mem Mapped IO PCSPGPRsIR mux Control IR I/O Port Timer, SFR’s Status Reset Vector Interrupt Vect RAM address data

CSE466 Autumn ‘00 Analysis  Bottleneck into and out of memory for data and code  Use of critical 8-bit address space (256) for memory mapped I/O and special function registers (timers and their controllers, interrupt controllers, serial port buffers, stack pointers, PC, etc). For example, the Motorola 6805 processor has only 187 RAM locations.  But, easy to program and debug. Compiler is simple too.

CSE466 Autumn ‘ : Modified Harvard Architecture ALU PC Internals Control Status Reset Vector Interrupt Vect RAM SFR’s (direct) Usually Stack (indirect) Bit Addressable Reg. Banks address mux data (indirect or Direct) 8051 standard + Enhancements PSW – 2-bits bank sel. 4x8 instruction 3 bits reg sel bits of reg. addr

CSE466 Autumn ‘ Memory Architecture  Advantages  Simultaneous access to Program and Data store  Register banks great for avoiding context switching on interrupt and for code compression  8-bit address space extended to = 384 registers by distinguishing between direct and indirect addressing for upper 128 bytes. Good for code compression  Bit addressable great for managing status flags  Disadvantage  A little bit confusing, with potential for errors.

CSE466 Autumn ‘00 Segments control address space…same in C NAMEexample PROGSEGMENTCODE CONSTSEGMENTCODE VAR1SEGMENTDATA BITVARSEGMENTBIT STACKSEGMENTIDATA RSEG BITVAR ; relocatable segment flag:DBIT 1; single bit variables RSEG VAR1 ; relocatable segment ih:DS 1; integer i is two bytes il:DS 1 RSEG STACK ; relocatable segment DS 10H ; 16 Bytes CSEG AT 0 ; absolute segment JMP START ; Execution starts here on reset. RSEG PROG ; relocatable segment START:MOV SP,#STACK-1 ; first set Stack Pointer MOV PSW,#00 ; use register bank O ;rest of main program here what would you add to include an interrupt routine? CSEG AT 0BH rti

CSE466 Autumn ‘00 Instruction Execution  6 States/Machine Cycle,  2 Osc. Cycles/State = 12 Cycles/Machine Cycle  Most instructions are 1 machine cycle, some are 2 or more  Can make two ROM accesses in on memory cycle (two byte/one cycle instructions, such as ADD A,#10H.  ALE – address latch enable, used when referencing external memory which can happen twice per machine cycle.  Its a Micro-coded CISC processor (sort of an old architecture)  Interesting features  No Zero flag (test accumulator instead)  Bit operations, Bit accessible RAM  Read Modify Write operations (ports)  Register to Register Moves  Multiply and Divide operations (many 8-bit MCU’s don’t have these)  Byte and Register Exchange operations  Register banks  Data pointer registers  Addressing Modes (careful when using upper 128 bytes of RAM)  BCD oriented instructions

CSE466 Autumn ‘00 Assembly Programming  Declare Segments and Segment types  Segments define what address space you are in.  Assembler converts to machine code, with relocatable segments.  Linker perform absolute code location  Segments  DATA -- Internal Data Address Space (0-7F direct or indirect)  IDATA -- Indirect Data Address Space (80-FF for stack, arrays) –Address is in R0 or R1  BIT – Bit addressable RAM space  XDATA -- External Data Address Space  CODE – Internal or external code space  CONST – Internal or external code space  Example Assembly Program

CSE466 Autumn ‘00 Last Term’s Lab MCU Atmel 89C55 +5V P2 Resistor Pack +5V Value on DIP switch controls LED frequency GND, VCC, XTAL, EA, Reset P1.1

CSE466 Autumn ‘00 Anatomy of an Assembly Program unsigned int i; void main (void) { register unsigned int tmp; while (1) { P1^= 0x01; i = 0; do { tmp = i; i += P2; } while (tmp < i); } Look for overflow in C – difficult to do Note i is global and tmp is local. What happens to local variables? How are registers used? What happens in a subroutine call?

CSE466 Autumn ‘00 Compiled C ?C0001:XRL P1,#01H CLR A MOV i,A MOV i+01H,A ?C0005: MOV R7,i+01H MOV R6,i MOV R5,P2 MOV A,R5 ADD A,i+01H MOV i+01H,A CLR A ADDC A,i MOV i,A CLR C MOV A,R7 SUBB A,i+01H MOV A,R6 SUBB A,i JC ?C0005 SJMP ?C0001 But, here is the optimized Compiled C

CSE466 Autumn ‘00 Now in Assembly RSEG PROG ; first set Stack Pointer START:MOV SP,#STACK-1 MOV PSW,#00 ; SET TO REG BANK O CLR flag ; just for show SETB flag ; just for show LOOP1:CLR C; Clear carry MOV A,il ; get low byte ADD A,P2; increment MOVil,A JNC LOOP1 ; loop until carry INC ih ; increment hi byte MOV A,ih ; check if zero JNZ LOOP1 ; XRL P1,#01H SJMP LOOP1 END NAMELab1_00sp PUBLICil PUBLICih PROGSEGMENTCODE ;CONSTSEGMENTCODE VAR1SEGMENTDATA BITVARSEGMENTBIT STACKSEGMENTIDATA RSEG BITVAR flag:DBIT 1 RSEG VAR1 ih:DS 1 il:DS 1 RSEG STACK DS 10H ; 16 Bytes CSEG AT 0 USING 0 ; Register-Bank 0 ; Execution starts at address 0 on power-up. JMP START

CSE466 Autumn ‘00 Embedded Hardware  Microcontrollers  Smallest: PIC 8-Pin (8-bit) PIC 8-pin MicrocontrollerPIC 8-pin Microcontroller  Middle: 6805 (8 bit) Example Flash Based 8051Example Flash Based 8051  Many 16-bit DSP Microcontrollers  HW support for MAC, Filter Algorithms  High End: StrongArm (32 bit) IntelIntel  Compare to pentium  External memory  Data Address Multiplexing  Memory Mapped I/O – talking to external devices  Typical Devices  Resistive Sensors (Strain, Temp, Gas, etc.)  Motion sensors (accelerometer)  Valve  Motor (Stepper, DC, Servo)\  Speaker  LCD Display  LED  Latches  Gas Sensors

CSE466 Autumn ‘00 Reset processor 1ms after powerup  1ms = 1/32 sec ~ 31ms  Let R = 10K, so C =.031/10K = 3.1uF RST 10K 3.2u what is the waveform on RST?

CSE466 Autumn ‘00 An output port Write Reg Pin bus

CSE466 Autumn ‘00 What’s Inside the Buffer? IhIh IlIl Write Reg This device always “drives” either high or low. Current is a function of pin voltage Never High Impedence ‘Z’ Note: this one inverts the signal, but its just an example…

CSE466 Autumn ‘00 A Bi-direction Port? Write Reg Read Reg Pin bus

CSE466 Autumn ‘00 I/O Ports Write Reg Read Reg Pin bus Dir Ctl Output driver can be disconnected from the pin so that input buffer can sense only the input signal This kind of bi-directional port requires a direction control register (SFR) for each bit of output (like StrongArm…

CSE466 Autumn ‘00 The 8051 (always has to be different) Eliminate the need for configuration bits by making outputs that can only drive strongly low (sink). There are three kinds of pins on the 8051 (of course) No pull up Weak pull up Weak pull up with momentary strong pullup To use a input pin, set output value to 1 (weak or no pullup). External signals just have to overpower the weak pull up (low resistance to ground). As output, will go from 0 to 1 slowly unless you add an external pullup Data sheet doesn’t spec the resistance of the pull up, but it specs the Amount of current that will result in a given voltage at the pin. For Example, in Ports 1,2,3 Ioh = -25uA at.75Vcc.

CSE466 Autumn ‘00 Application: Wired NOR 8051 Communication bus: Each processor tries to send data, but detects collision. If collision, then stop transmitting Collisions are safe because nobody drives high. The one who writes the zero first gets the bus! Q1) How can a processor detect a collision?

CSE466 Autumn ‘00 Summary  Port 0:  used as address bus for external address/data bus. Uses active pullup in this mode. Fast  Can use as GPIO. Must use external pullup. Pullup size is power/speed tradeoff, up to 3.2mA  Port 1 and 3:  GPIO only. External pullups are optional. Power/speed tradeoff, up to 1.6mA.  Port 2:  Also used for external address bus. Has active and passive internal pullups. External pullups are optional in GPIO mode, up to 1.6mA.

CSE466 Autumn ‘00 Example Problem P1 Open = 0 Closed = 1 R 1) As big as possible! According to Data sheet: Processor reads a zero if Vpin <.2Vcc -.3 = 0.7V I low (port 1) is.45Vp at 50uA. So what is max R? (.45/50e-6) = 9Kohms So the switch resistor better be smaller than 9Kohms. 4.7K is a good choice. 2.7 is okay but higher power! Vp

CSE466 Autumn ‘00 Careful w/ Coils (motors, etc) Current limiter R = 50Ohms Coil (L) MOSFET Switch 8051 Steady state on current: Vcc/R Vds ~ 0 (Rds ~ 4mOhm) But, when we try to turn off the Mosfet quickly, what happens? Rds goes up quickly, but Ids drops slowly) If Rds becomes 1K, then Vds becomes 100V And instantaneous power becomes 10W I =0.1A Vds

CSE466 Autumn ‘00 I/O Ports  Input ports: Hi Input impedance (like CMOS transistor gate)  Output ports: Hi drive (current source/sink) capability (like CMOS transistor channel)  Bidirectional Ports?  Weak Pullup Approach used in the 8051  Configuration bits (used in other MCU’s)

CSE466 Autumn ‘00 Basic Electronics  Speaker Interface. Design a direct drive circuit for the speakers. How much power are we dissipating in the speaker if we stay within current rating of chip?  How can we get more power to the speaker?  Note to self: Saturation v. Linear operation

CSE466 Autumn ‘00 Design Meeting – Speaker Driver  Problems  multiple tones  amplification