Slide 1: Microcontroller
8051 Contents: : Contents: Introduction
Block Diagram and Pin Description of the 8051
Memory mapping in 8051
Stack in the 8051
I/O Port Programming
Interrupt Why do we need to learn Microprocessors/controllers? : Why do we need to learn Microprocessors/controllers? The microprocessor is the core of computer systems.
Nowadays many communication, digital entertainment, portable devices, are controlled by them.
A designer should know what types of components he needs, ways to reduce production costs and product reliable. Different aspects of a microprocessor/controller : Different aspects of a microprocessor/controller Hardware :Interface to the real world
Software :order how to deal with inputs The necessary tools for a microprocessor/controller : The necessary tools for a microprocessor/controller CPU: Central Processing Unit
I/O: Input /Output
Bus: Address bus & Data bus
Memory: RAM & ROM
Parallel Port Microprocessors: : CPU
General-Purpose Micro-processor RAM ROM I/O Port Timer Serial COM Port Data Bus Address Bus General-Purpose Microprocessor System Microprocessors: CPU for Computers
No RAM, ROM, I/O on CPU chip itself
Example：Intel’s x86, Motorola’s 680x0 Many chips on mother’s board General-purpose microprocessor Slide 7: RAM ROM I/O Port Timer Serial COM Port Microcontroller CPU A smaller computer
On-chip RAM, ROM, I/O ports...
Example：Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X A single chip Microcontroller : Slide 8: Microprocessor
CPU is stand-alone, RAM, ROM, I/O, timer are separate
designer can decide on the amount of ROM, RAM and I/O ports.
CPU, RAM, ROM, I/O and timer are all on a single chip
fix amount of on-chip ROM, RAM, I/O ports
for applications in which cost, power and space are critical
single-purpose Microprocessor vs. Microcontroller Slide 9: Embedded system means the processor is embedded into that application.
An embedded product uses a microprocessor or microcontroller to do one task only.
In an embedded system, there is only one application software that is typically burned into ROM.
Example：printer, keyboard, video game player Embedded System Slide 10: meeting the computing needs of the task efficiently and cost effectively
speed, the amount of ROM and RAM, the number of I/O ports and timers, size, packaging, power consumption
easy to upgrade
cost per unit
availability of software development tools
assemblers, debuggers, C compilers, emulator, simulator, technical support
wide availability and reliable sources of the microcontrollers. Three criteria in Choosing a Microcontroller Block Diagram : Block Diagram CPU On-chip RAM On-chip ROM for program code 4 I/O Ports Timer 0 Serial Port OSC Interrupt Control External interrupts Timer 1 Timer/Counter Bus Control TxD RxD P0 P1 P2 P3 Address/Data Counter Inputs Slide 13: Pin Description of the 8051 Pins of 8051（1/4） : Pins of 8051（1/4） Vcc（pin 40）：
Vcc provides supply voltage to the chip.
The voltage source is +5V.
XTAL1 and XTAL2（pins 19,18） Slide 15: Figure (a). XTAL Connection to 8051 Using a quartz crystal oscillator
We can observe the frequency on the XTAL2 pin. Pins of 8051（2/4） : Pins of 8051（2/4） RST（pin 9）：reset
It is an input pin and is active high（normally low）.
The high pulse must be high at least 2 machine cycles.
It is a power-on reset.
Upon applying a high pulse to RST, the microcontroller will reset and all values in registers will be lost.
Reset values of some 8051 registers Figure (b). Power-On RESET Circuit : Figure (b). Power-On RESET Circuit 30 pF 30 pF 8.2 K 10 uF + Vcc 11.0592 MHz EA/VPP X1 X2 RST 31 19 18 9 Pins of 8051（3/4） : Pins of 8051（3/4） /EA（pin 31）：external access
There is no on-chip ROM in 8031 and 8032 .
The /EA pin is connected to GND to indicate the code is stored externally.
/PSEN ＆ ALE are used for external ROM.
For 8051, /EA pin is connected to Vcc.
“/” means active low.
/PSEN（pin 29）：program store enable
This is an output pin and is connected to the OE pin of the ROM. Pins of 8051（4/4） : Pins of 8051（4/4） ALE（pin 30）：address latch enable
It is an output pin and is active high.
8051 port 0 provides both address and data.
The ALE pin is used for de-multiplexing the address and data by connecting to the G pin of the 74LS373 latch.
I/O port pins
The four ports P0, P1, P2, and P3.
Each port uses 8 pins.
All I/O pins are bi-directional. Pins of I/O Port : Pins of I/O Port The 8051 has four I/O ports
Port 0 （pins 32-39）：P0（P0.0～P0.7）
Port 1（pins 1-8） ：P1（P1.0～P1.7）
Port 2（pins 21-28）：P2（P2.0～P2.7）
Port 3（pins 10-17）：P3（P3.0～P3.7）
Each port has 8 pins.
Named P0.X （X=0,1,...,7）, P1.X, P2.X, P3.X
Ex：P0.0 is the bit 0（LSB）of P0
Ex：P0.7 is the bit 7（MSB）of P0
These 8 bits form a byte.
Each port can be used as input or output (bi-direction). Hardware Structure of I/O Pin : Hardware Structure of I/O Pin Each pin of I/O ports
Internal CPU bus：communicate with CPU
A D latch store the value of this pin
D latch is controlled by “Write to latch”
Write to latch＝1：write data into the D latch
2 Tri-state buffer：
TB1: controlled by “Read pin”
Read pin＝1：really read the data present at the pin
TB2: controlled by “Read latch”
Read latch＝1：read value from internal latch
A transistor M1 gate
Gate=1: close D Latch: : D Latch: A Pin of Port 1 : A Pin of Port 1 8051 IC P0.x Writing “1” to Output Pin P1.X : Writing “1” to Output Pin P1.X 8051 IC 2. output pin is Vcc 1. write a 1 to the pin 1 0 output 1 TB1 TB2 Writing “0” to Output Pin P1.X : Writing “0” to Output Pin P1.X 8051 IC 2. output pin is ground 1. write a 0 to the pin 0 1 output 0 TB1 TB2 Reading “High” at Input Pin : Reading “High” at Input Pin 8051 IC 2. MOV A,P1
external pin=High write a 1 to the pin MOV P1,#0FFH 1 0 3. Read pin=1 Read latch=0 Write to latch=1 1 TB1 TB2 Reading “Low” at Input Pin : Reading “Low” at Input Pin 8051 IC 2. MOV A,P1
external pin=Low write a 1 to the pin
MOV P1,#0FFH 1 0 3. Read pin=1 Read latch=0 Write to latch=1 0 TB1 TB2 Other Pins : Other Pins P1, P2, and P3 have internal pull-up resisters.
P1, P2, and P3 are not open drain.
P0 has no internal pull-up resistors and does not connects to Vcc inside the 8051.
P0 is open drain.
Compare the figures of P1.X and P0.X.
However, for a programmer, it is the same to program P0, P1, P2 and P3.
All the ports upon RESET are configured as output. A Pin of Port 0 : A Pin of Port 0 8051 IC P1.x Port 0 with Pull-Up Resistors : Port 0 with Pull-Up Resistors Port 3 Alternate Functions : Port 3 Alternate Functions RESET Value of Some 8051 Registers: : RESET Value of Some 8051 Registers: 0000 DPTR 0007 SP 0000 PSW 0000 B 0000 ACC 0000 PC Reset Value Register RAM are all zero. Slide 33: Registers Memory mapping in 8051 : Memory mapping in 8051 ROM memory map in 8051 family 4k DS5000-32 8k 32k from Atmel Corporation from Dallas Semiconductor Slide 35: RAM memory space allocation in the 8051 Stack in the 8051 : Stack in the 8051 The register used to access the stack is called SP (stack pointer) register.
The stack pointer in the 8051 is only 8 bits wide, which means that it can take value 00 to FFH. When 8051 powered up, the SP register contains value 07. Timer : : Timer : TMOD Register: : TMOD Register: Gate : When set, timer only runs while INT(0,1) is high.
C/T : Counter/Timer select bit.
M1 : Mode bit 1.
M0 : Mode bit 0. TCON Register: : TCON Register: TF1: Timer 1 overflow flag.
TR1: Timer 1 run control bit.
TF0: Timer 0 overflag.
TR0: Timer 0 run control bit.
IE1: External interrupt 1 edge flag.
IT1: External interrupt 1 type flag.
IE0: External interrupt 0 edge flag.
IT0: External interrupt 0 type flag. Interrupt : : Interrupt : Interrupt Enable Register : : Interrupt Enable Register : EA : Global enable/disable.
--- : Undefined.
ET2 :Enable Timer 2 interrupt.
ES :Enable Serial port interrupt.
ET1 :Enable Timer 1 interrupt.
EX1 :Enable External 1 interrupt.
ET0 : Enable Timer 0 interrupt.
EX0 : Enable External 0 interrupt.