User guide

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User Guide V1.10
The following target system requirements must be met for the Gemini-1 programmer to
reliably in-system program (ISP) a target microcontroller:
Target Oscillator
The ISP mode of the TEMIC microcontroller uses a ‘Boot Loader’ stored in the target
microcontroller. It follows, therefore, that the target microcontroller must be able to execute
the ‘Boot Loader’ firmware. The speed at which the ‘Boot Loader’ firmware is executed
depends on the target oscillator frequency.
To ensure the fastest and most reliable ISP operation, the target oscillator frequency should
be chosen to be the highest value possible within the specification of the device. It is not
necessary to choose a frequency which gives an exact ‘Baud rate’ as the ‘Boot Loader’ is
capable of auto-detecting most baud rates and compensating accordingly.
Target System Requirements
PROG_ACTIVE Polarity
The PROG_ACTIVE line can be used to warn the target
microcontroller that the RESET pin is about to be
asserted. If an LED on the target system is connected
to the PROG_ACTIVE line of the programmer, the
polarity should be set to ‘Active LOW’. The LED will
illuminate when the programmer asserts the
PROG_ACTIVE line at the start of the programming
sequence.
PROG_ACTIVE
Vcc
R1
Figure 32