BIN Hardware Block Diagram
The hardware arrangement can be represented in simplified form as a block diagram (Figure 3.2). This is not really necessary for such a trivial circuit, but is a useful system design technique for more complex applications. The main parts of the hardware and relevant inputs
and outputs should be identified, together with the direction of signal flow. The type of signal can be indicated, e.g. parallel or serial data, or analogue waveform. The power connections need not be shown; it is assumed that suitable supplies are available for the active components. The idea is to outline the basic hardware arrangement without having to design the circuit in detail at this stage.
Port A (5 bits) and port B (8 bits) give access to the data registers of the ports, the pins being labelled RA0 to RA4, and RB0 to RB7, respectively. The two push-button switches will be connected to RA0 and RA1, and a set of LEDs connected to RB0 to RB7. The switches will later be used to control the output sequence. However, these inputs will not be used in the first program, BIN1. The connections required are shown in Table 3.2.
The block diagram can now be converted into a circuit diagram. A drawing is created using electronic schematic capture software such as Proteus VSM (ISIS) or ORCAD. In Proteus, the design file can then be used to test the circuit by interactive simulation. When finalized, it can be converted into a printed circuit board and the hardware produced. The schematic can be inserted into other documentation as required, or printed separately.
The schematic for the BIN circuit design created in ISIS (BIN.DSN) is shown in Figure 3.3. This is available on the support website www.picmicros.org.uk and can be used to simulate the circuit operation described below. The process for editing the schematic and simulating the circuit operation is described in Appendix E. The operation of the chip itself can be simulated in MPLAB, the Microchip development system.