2 Hardware

The processor-containing board communicates with external devices through a 96-pin bus connector. On this connector there are pins for the address bus, the data bus and all important control signals. All our communication is performed in the synchronous memory area (F0000-F3FFF), why only the pins for address, data and signals VMA, E, RESET and R/W are used.

L A14 + + - - A16

A3 A2 A12 E RES A1 A0 + + - -

A4 A5 A6 A7 A8 A9 A10 A11 A13 + + - -

A15 A18 A19 D3 D2 + + - -

A17 D0 D6 VMA + + - -

RW D7 D4 D5 D1 + + - -

96-polig bus connector (only used pins marked here)

2.1 PIA

(Peripheral Interface Adapter)

The PIA is used as interface between the microcomputer and the external units, plotter and hexboard. The inport is a 8-bit wide data bus, and the outports are two 2-way, 8-bit wide data buses.

2.2 Display

The display (Hewlett Packard HDSP-2112) has a character window, which is capable of showing at chars simultaneously. The charset consists of 128 ASCII and 16 user-defined. Choice of position within the char window is made through a 3-bit address.

2.3 Keyboard

The keyboard is hexadecimal, with the keys 0 to F. The outport is 4 databits and a strobe, which goes high when a key is pressed.

2.4 Plotter

The plotter movement is actuated by 2 4-phase step motors. The pulse sequence for forward movement is given below.

rad x0/y0 x3/y3 x1/y1 x2/y2

1 1

2 1 1

3 1

4 1 1

5 1

6 1 1

7 1

8 1 1

Table: Pulse sequence

Each step in the table means a movement of 0.05 mm at the pen tip. The inport of the plotter is 8 bits for the step motors and extra bits for signals. One of the signals is used to lower/raise the pen.

2.5 Blockchart

The components are put together as shown in the chart.

Blockchart over the hardware.