MICROCONTROLLER .pptx
- 1. MICROCONTROLLER Unit II -ASSEMBLY PROGRAMMING AND INSTRUCTION OF 8051 Lecture – 12
- 2. UNIT – II ASSEMBLY PROGRAMMING AND INSTRUCTION OF 8051 Introduction to 8051 assembly programming, Assembling and running an 8051 program, Data types and Assembler directives, 8051 Addressing Modes, Arithmetic, logic instructions and programs, Jump, loop and call instructions, I/O port programming.
- 4. Port 0 Port 0 occupies a total of 8 pins (pins 32–39). It can be used for input or output. To use the pins of port 0 as both input and output ports, each pin must be connected externally to a 10Kohm pull-up resistor. This is due to the fact that P0 is an open drain, unlike P1, P2, and P3.
- 5. With resistors connected to port 0, in order to make it an input, the port must be programmed by writing 1 to all the bits. In the following code, port 0 is configured first as an input port by writing 1s to it, and then data is received from that port and sent to P1. ;Get a byte from P0 and send it to P1 MOV A,#0FFH ;A = FF hex MOV P0,A ;make P0 an input port by writing all 1s to it BACK: MOV A,P0 ;get data from P0 MOV P1,A ;send it to port 1 SJMP BACK ;keep doing it Dual role of port 0 As shown in Figure 1, port 0 is also designated as AD0–AD7, allowing it to be used for both address and data. When connecting an 8051/31 to an external memory, port 0 provides both address and data. The 8051 multiplexes address and data through port 0 to save pins.
- 6. Port 1 Port 1 occupies a total of 8 pins (pins 1 through 8). It can be used as input or output. In contrast to port 0, this port does not need any pull-up resistors since it already has pull-up resistors internally. Upon reset, port 1 is configured as an input port. The following code will continuously send out to port 1 the alternating values 55H and AAH. ;Toggle all bits of P1 continuously MOV A,#55H BACK: MOV P1,A ACALL DELAY CPL A ;complement(Invert) reg. A SJMP BACK
- 7. Port 2 Port 2 occupies a total of 8 pins (pins 21 through 28). It can be used as input or output. Just like P1, port 2 does not need any pull-up resistors since it already has pull-up resistors internally. Upon reset, port 2 is configured as an input port. The following code will continuously send out to port 2 the alternating values 55H and AAH. That is, all the bits of P2 toggle continuously. MOV A,#55H BACK: MOV P2,A ACALL DELAY CPL A ;complement reg. A SJMP BACK
- 8. ;Toggle all bits of P0 BACK: MOV A,#55H MOV P0,A ACALL DELAY MOV A,#0AAH MOV P0,A ACALL DELAY SJMP BACK By sending 55H and AAH to a given port continuously, we toggle all the bits of that port. Dual role of port 2 In many systems based on the 8051, P2 is used as simple I/O. However, in 8031-based systems, port 2 must be used along with P0 to provide the 16-bit address for external memory. Port 2 is also designated as A8–A15, indicating its dual function.