PIC Microcontroller

To a computer or microprocessor, the world is seen in terms of patterns of digits. The decimal (or denary) system represents quantities in terms of the ten digits 0.. .9. Together with the judicious use of the symbols +, -and . any quantity in the range ±™ can be depicted. Indeed non-numeric concepts can be […]

Digital Representation Part 2 (PIC Microcontroller)

Both the examples involve adding an 8-bit to a 16-bit operand. Where the former is positive, the data may be increased to 16 bits by padding with 0s. The situation is slightly less intuitive where negative data requires extension. Here the prescription is to extend the data by padding out with 1 s. In the […]

Logic Circuitry Part 1 (PIC Microcontroller)

We have noted that digital processing is all about transmission, manipulation and storage of binary word patterns. Here we will extend the concepts introduced in the last topic as a lead into the architecture of the computer and microprocessor. We will look at some relevant logic functions, their commercial implementations and some practical considerations. After […]

Logic Circuitry Part 2 (PIC Microcontroller)

As we shall see, the ALU is the heart of the computer and microprocessor architectures. By feeding the Select inputs with a series of mode words, a program of operations can be performed by the ALU. Such operation codes are stored in an external memory, and are accessed sequentially by the computer’s control circuits. Sequences […]

Logic Circuitry Part 3 (PIC Microcontroller)

There are many bistable implementations. For example, replacing the NOR gates by NAND gives a RS latch, where the inputs are active on a logic 0. The circuit illustrated in Fig. 2.14 shows such a latch used to de-bounce a mechanical switch. Manual switches are frequently used as inputs to logic circuits. However, most metallic […]

Logic Circuitry Part 4 (PIC Microcontroller)

T flip flops can of course be cascaded, as shown in Fig. 2.22(a). Here four ^ triggered flip flops are chained, with the output of binary n clocking binary n + 1. Thus if the input Count frequency was 8 KHz, then Qa would be a 4 kHz square waveform and similarily QB would measure […]

Stored Program Processing Part 1 (PIC Microcontroller)

If we take the Arithmetic Logic Unit (ALU) Working register pair depicted in Fig. 2.19  and feed it with function codes, then we have in essence a programmable processing unit. These command codes may be stored in digital memory and constitute the system’s program. By fetching these instructions down one at a time we can […]

Stored Program Processing Part 2 (PIC Microcontroller)

Although our program doesn’t do very much, it only takes around 1 ^s to implement each instruction. A million unimpressive operations each second can amount to a great deal! Nevertheless, it hardly rates highly in the annals of software, so we will wrap up our introduction to computing by looking at some slightly more sophisticated […]

Stored Program Processing Part 3 (PIC Microcontroller)

File Indirect Indirect addressing uses an address register to hold the address of an operand. This address register thus acts as a pointer into the Program store. The term indirect is used as this address register does not hold the operand datum itself, only a pointer address to it. The advantage of this seemingly perverse […]

Stored Program Processing Part 4 (PIC Microcontroller)

Solution Although BASIC is only capable of directly implementing 8-bit arithmetic, operations of any length are possible by breaking down the process into byte-sized chunks. In the case of addition, this involves a sequence of byte operations from the least to the most significant digits with any carry from the nth digit byte being added […]