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User Guide V1.10

Implementation of ISP on the target system

The circuit schematic shown in figure 29 details the connections required between the

programmer and the target 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. P89C51Rx+, P89C51Rx2 -

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

See Note 1

R1 LED current limiting resistor (optional) 2k7 Ohms

R2 Used to discharge C5 when the Vpp (+12V) 22k Ohms

is removed.

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

C5 Vpp decoupling capacitor 47n Farads

D1 Programmer ‘Active’ LED LED -

D2 Diode to prevent the Vpp (+12V) from eg. 1N4148 -

affecting the Vcc supply

XT1 Crystal Oscillator See datasheet for chosen target MHz

microcontroller

J1 Optional jumper For P89C51Rx+ targets -

Fitted - connects PROG_VPP from (Vpp = +12V): J1 - fitted

programmer to EA/Vpp pin of target For P89C51Rx2 targets:

microcontroller (Vpp =+5V): J1 - Not fitted

Not fitted - completely isolates +12V Vpp

from the target microcontroller.

J2 Optional jumper For P89C51Rx+ targets -

For P89C51Rx2 devices, the EA/Vpp pin can (Vpp = +12V): J1 - NOT fitted

be connected directly to Vcc For P89C51Rx2 targets:

(Vpp =+5V): J1 - fitted

Circuit Description / purpose Recommend Value Units

Label

ISP Target System Design Guide - Philips Microcontrollers

Figure 28

1 2 ... 36 37 38 39 40 41 42 43 44 45 46 ... 57 58

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Equinox Systems GEMINI Guide de l'utilisateur Page 41