The Device Programmer consists of two parts ... The In-Circuit Debugging Interface
The Device Programmer includes a socket ( DIL1 ) into which an AT90S1200 or
AT90S1200A processor ( IC1 ) can be plugged to be programmed from a PC.
A crystal oscillator ( XTAL1, C1 and C2 ) is included for the AT90S1200
processors which do not use an internal RC clock; the frequency of the
crystal should be chosen to match the speed of the processor which you are
programming. Rather than have a complex arrangement for selecting various
types of crystal, it makes sense to build a separate programmer for
each processor clock speed required although a switching arrangement could
be built. Capacitors C1 and C2 may need to be adjusted to match the particular
crystal. All the processor lines ( with the exception of the two crystal oscillator
lines, X1 and X2 ) are taken to a 25-way, Cannon-D, Female socket ( SKT1 ) so
the programmed chip can be used to control target hardware ( with a suitable
interface ) directly from the chip in the Device Programmer. This interface
also allows the Development Hardware Add-Ons to be
connected to the Device Programmer.
An external DC power supply ( +5v maximum ) may be connected to Pin 25 of SKT1
so that the processor may be used when disconnected from the PC; this would
normally be the case when the Device Programmer is plugged into target
hardware and the supply voltage is delivered from the target hardware itself.
A diode ( D1 ) is used to prevent problems when any conected target hardware is
powered down.
The PC Programming Interface
The PC programming interface allows the processor ( IC1 ) to be programmed
directly from a PC. A processor in the target hardware ( with a suitable
interface ) can also be programmed via the In-Circuit Debugger
Interface ( with the processor chip removed ).
The Device Programmer is connected to a line printer port on the programming PC
through a 25-way, Cannon-D, Male socket ( SKT2 ).
Resistors R3 to R7 are used to deliver power to the processor during the loading
of code and its execution. These provide current limiting and protect the five
data lines from the parallel port from damage. A diode ( D2 ) is included to
allow an external power supply to be connected to the Device Programmer.
A capacitor ( C3 ) is included to smooth the power supply and prevent noise on
the power supply whilst a LED indiactor ( R1 and L1 ) is used to show when
power is supplied to the processor ( IC1 ) and acts as a visible, "Do not
remove chip", warning. Resistors ( R2 and R8 ) are used to current imit the signals from the two data
lines of the parallel port which are used to program the processor.
Operation
The In-Circuit Debugging Interface does little more than allow the connections
of the processor to be connected to target hardware or Development Hardware
Add-Ons so that code executing in the processor can control hardware external
to the Device Programmer.Much of this interface can be ignored if you do not wish to use the device
programmer to program or control target hardware or the Development Hardware
Add-Ons are not going to be used. The PC Programming Interface allows the processor to be connected and programmed
from a standard PC line printer port. --MORE--
Schematics
Schematic ( Part 1 ) - The In-Circuit Debugging Interface
Schematic ( Part 2 ) - The PC Programming Interface
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