User guide

User Guide V1.10

Implementation of ISP on the target system

The circuit schematic shown in figure 31 details the connections required between the

programmer and the TEMIC T89C51Rx2 microcontroller. Some connections and components

are optional depending on the device family being used and whether a ‘PROGRAMMER

ACTIVE’ LED is required on the target system.

U1 Target 89C ISP microcontroller eg. T89C51Rx2 -

U2 RS-232 Transceiver IC (optional) eg. MAX232 -

See Note 1

R1 LED current limiting resistor (optional) 2k7 Ohms

R3 This resistor prevents output clashes 4k7 Ohms

between the PROG_TXD pin and the output

of the RS-232 Transceiver IC. (optional)

C1 Oscillator capacitor 33p Farads

C2 Oscillator capacitor 33p Farads

C3 Supply decoupling capacitor 1u Farads

C4 Supply decoupling capacitor 100n Farads

D1 Programmer ‘Active’ LED LED -

XT1 Crystal Oscillator See datasheet for chosen target MHz

microcontroller

J2 Optional jumper - -

For T89C51Rx2 devices, the EA/Vpp pin

should be connected directly to Vcc.

Circuit Description / purpose Recommend Value Units

Label

Figure 30

ISP Target System Design Guide - TEMIC Microcontrollers