User guide

User Guide V1.10
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Overview
The Philips P89C51Rx+, P89C51Rx2 and TEMIC T89C51Rx2 microcontroller families feature
on-chip FLASH CODE memory which may be in-system programmed (ISP) using the Gemini
ISP programmer. To facilitate ISP on your target system, it is necessary for you to bring out
certain connections from the target microcontroller to a header on your PCB. The Gemini ISP
cable plugs into this header allowing the programmer to assert the correct signals.
Notes:
• The programmer requires a minimum of five connections to the target system to facilitate
In-System Programming (TXD, RXD, GROUND, VCC & Vpp).
• The programmer draws power from the target system.
• The programmer features an on-board Vpp generator circuit (i.e. The target system does
not have to generate the Vpp voltage)
• The programmer communicates with the target microcontroller using the 8051 UART
(Serial Port).
• The programmer forces the target microcontroller into ‘ISP’ mode using the ‘Hardware
Activation of the Boot Loader’ technique - ‘IAP’ mode is NOT supported.
• The target microcontroller can execute code when the programmer is connected or
disconnected from the target system.
Target System - ISP Design Requirements
User
Target
System
PC
GEMINI-1
External
Devices
1
2 3
1 Earth connection to PC
2 Target system earth
3 Earth from external device
Common earthing point
Serial Cable
Figure 24