Equinox Systems GEMINI Podręcznik Użytkownika Pobierz pdf (Strona 44)

User Guide V1.10

RS-232 Transceiver

The Gemini programmer utilises ‘logic level’ signals on the ‘PROG_RXD’ and ‘PROG_TXD’

lines. This allows the programmer to be connected to the target system with no need for a

costly RS-232 Transceiver IC. However, if your target system uses the UART of the target

microcontroller during normal operation, it is likely that you will be using an RS-232

Transceiver IC on your board to drive the target serial port. If this is the case, it is necessary

to insert a resistor, R3, in the ‘PROG_TXD’ line as shown in the circuit schematic. This

resistor allows both the programmer and the Transceiver IC to drive the microcontroller

RXD pin without contention.

Port 2.7

It is imperative that Port P2.7 is not tied to ground. This pin can be used as a ‘user input’

as long as it is high when the target microcontroller is in RESET.

ISP Target System Design Guide - Philips Microcontrollers

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Equinox Systems GEMINI Podręcznik Użytkownika Strona 44