8051 Microcontroller Architecture By Er. Swapnil V. Kaware, Lecture notes of Microcontrollers

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8051 Microcontroller

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Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

8051 Microcontroller

Presented By,

Er. Swapnil V. Kaware,

B.E. (Electronics), M.E. (Electronics)

svkaware@yahoo.co.in

2 Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

(6). 128 bytes internal RAM (data). (7). Four 8-bit I/O ports. (8). Two 16-bit timers. (9). Serial interface Communication. (10). 64K external code & data memory space. 4 Salient Features Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

(11). 210 bit-addressable locations.

(12). Internal memory consists of on-chip ROM and on-

chip data RAM.

(13). 8051 implements a separate memory space for

programs (code) and data.

(14). Operating frequency is 24MHz-33MHz.

(15). +5V Regulated DC power supply is required to

operate.

(16). It has four 8 bit ports, total 32 I/O lines.

5 Salient Features

8051 Block Diagram 7

Internal Architecture

Oscillator Circuit:-

(1). The 8051 requires an external oscillator circuit.

(2). The oscillator circuit usually runs around 12MHz.

(3). The crystal generates 12M pulses in one second.

(4). The pulse is used to synchronize the system operation

in a controlled pace.

8 Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

Internal Memory

(1). 8051 implements a separate memory space for

programs (code) and data.

(2). Both code and data may be internal, however, both

expand using external components to a maximum of

64K code memory and 64K data memory.

(3). Internal memory consists of on-chip ROM and on-chip

data RAM.

10 Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

(4). On-chip RAM contains a rich arrangement of general

purpose storage, bit addressable storage, register

banks, and special function registers.

(5). In the 8051, the registers and input/output ports are

memory mapped and accessible like any other memory

location.

(6). In the 8051, the stack resides within the internal RAM,

rather than in external RAM.

11 Internal Memory Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

13 Register banks in the 8051 Microcontroller

Special Function Registers

(1). ACC

(2). B

(3). PSW

(4). SP

(5). DPTR

(5). IP

(6). PMODE

(7). PCON

(8). TMODE

(9). TCON etc.

14

B Register (1). B register or accumulator B is used along with the accumulator for multiply and divide operations. (2). MUL AB: multiplies 8 bit unsigned values in A and B. and leaves the 16 bit result in A (low byte) and B (high byte). (3). DIV AB: divided A by B, leaving the integer result in A and remainder in B. (4). B register is bit-addressable. 16 Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

17 PSW (Program Status word) / Flag Register

(6). 8051 stack is kept in the internal RAM.

(7). Depending on the initial value of the SP, stack can

have different sizes.

(8). Example: MOV SP,#5FH.

(9). On 8051 this would limit the stack to 32 bytes

since the uppermost address of on chip RAM is 7FH.

19 Stack Pointer Microcontroller Notes by Er. Swapnil V. Kaware (svkaware@yahoo.co.in)

Data pointer (DPTR) (1). Data pointer (DPTR): is used to access external data or code. (2). DPTR is a 16 bit register at addresses 82H (low byte) and 83H (high byte). (3). The data pointer is used in operations regarding external RAM and some instructions involving code memory. (4). Example: the following instructions write 55H into external RAM location 1000H:

• MOV A,#55H
• MOV DPTR,#1000H
• MOVX @DPTR,A 20