EMDP1 — Extensible Multiple Device Programmer 1 (Rev. C) using pic microcontroller

Table of Contents

• Table of Contents
• Introduction
• Schematics
• Printed Circuit Board
• Issues

Introduction

This is revision C of the EMDP1 mother board. It differs from revision B in that a 40-pin ZIF (zero insertion force) socket and an 80-pin `universal’ plug have been added. This allows many chips to be programmed without requiring an adaptor board. When the `universal’ plug is not enough, a specialized adaptor board may be employed.

Schematics

The parts list is kept in a separate file.

The power supply takes its power from either the SimpliciNet RJ45 connector N4 (shown as the wire labeled PWR) or from a wall wart connector, either N1 (on-board) or N10 (off-board). The on-off-on switch SW1 chooses between the two possible power sources. Diode D1 is a shorting diode that should short the supply and burn out the fuse F1 9on-board) or N3 (off baord fuse) if power somehow gets applied backwards. The C1, U1, C2 combination is a standard low voltage linear 5 volt supply using an LM2940 low drop out voltage regulator. The rest of the circuitry revolves around U2, µA78S40 switching supply chip which generates 24 volts from the input voltage of 6 volts. The design equations for the switching supply chip are in the appendix of the main EMDP1 design document.

The EMDP1 can communicate with its host processor via either RS-232 or RS-422 signaling. The RS-232 signaling takes place via an industrys standard female DB9 connector. The RS-422 signaling done via an RJ45 connector using standard Cat5 (catagory 5) cabling. The RS-422 is wired to conform to my SimpliciNet `standard’, which allows both RS-422 signalling and power over the same cable.

The RS-232 signals are converted to logic levels using U3, a standard MAX232 level convert chip. U4 is an RS-422 transceiver configured as an RS-422 transmitter and U5 is an RS-422 transceiver configured as a receiver. Resister R7 is 100 ohms of RS-422 termination and R8 and R9 provide biasing resistors to ensure that a logic high level is output if now RS-422 signal is present. U6A is takes the logical or of the received signals from the RS-232 and RS-422 and sends them on to the microcontroller serial receive line. U6B logically or’s the transmit signals from the adaptor (via U11A) or from the microcontroller (MTX). R27 is forces the adaptor signal out if the microcontroller chip is being programmed by the bootstrap adaptor.

For more detail: EMDP1 — Extensible Multiple Device Programmer 1 (Rev. C)