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Commodore PET Projects - petSD+

petSD+ - User Guide


Connection / Disconnection
* * * Power OFF the PET/CBM and petSD+ before connecting or disconnecting petSD+ from the computer * * *
SD Card Insertion / Removal
* * Ensure that the Card Access LED (see below) is OFF before installing or removing the SD Card * *

User Controls & Indicators

The photo shows a fully featured petSD+, fitted with the Real Time Clock and LCD components, as well as a standard IEEE-488 connector.

The LCD has been removed for clarity, to show the position of the controls and indicators on the PCB.


Reset Switch

All versions of petSD+ have a Reset push-button (S1) located at the rear of the unit, close to the power connector, although, depending on how you mount the internal version, you may not have access to the Reset push-button and you may need to power cycle the computer in the unlikely event that you need to reset petSD+.


Internal petSD+

Internal models have two bit-switches (SW2-1 & SW2-2) installed, located at the front of the unit, close to the SD Card slot. These are used to set the Device Address, the default position, with both switches OFF, sets Device Address 8. All other user interaction with petSD+ is through Commodore BASIC and/or the DOS Wedge.

The internal model has no LCD or menu control buttons fitted and the IEEE-488 connector is replaced by 1 (PCB Version 2) or 2 (PCB Version 1) IDC cable sockets.
There is normally ample space inside a PET to install petSD+.

This photo shows petSD+ installed adjacent to the system board at the front left of a model 8032 PET. The blue ribbon cable connects petSD+ to a header plug on the IEEE-488 internal connector, J12.

Note : whilst only 24 pins are needed for internal connection, I normally fit a 26 way IDC connector to petSD+ as 26 way IDC cables are much easier to source than 24 way.

(Internal petSD+ mounting Photos courtesy of Robert Henke)

Close up of the installed petSD+

It is not obvious from the photo, but the IDC cable has 26 cores which leaves two spare pin positions which overhang the 24 way header on the PET PCB.
J12 is located close to the IEEE-488 "finger" connector, but is usually not fitted with a header. Here, you can see the 12x2 0.1" header that Robert has soldered to the PET system board, ready for attaching petSD+ . . . . .
 . . .now with the ribbon cable connected.

Note: The pin-header does not have a "key" and care must be taken to ensure that the cable is orientated correctly, with Pin 1 of the plug connected to Pin 1 on the header. In future, I think that I will supply a keyed socket for users who purchase an internal model to reduce the risk of connecting the cable wrongly, although no damage should result if that were to happen.
The only other consideration is how to provide power to petSD+. There are a number of ways of picking up 5VDC off the computer board, here, Robert has chosen to solder the wires from the petSD+ power connector directly to the "fingers" of the cassette port connector.



External petSD+

Rear view of a typical Commodore CBM/PET, showing the expansion port connectors.

This is a Model 8296, but most models are similar in layout.
 In this case, the IEEE-488 connector is positioned close to the centre of the rear panel - directly below the serial number label. On most PET/CBMs, the I/O ports are unlabeled, looking from the rear, the IEEE-488 connector is usually the one on the right hand side, closest to the power cord. (The IEEE port is usually identified as "J1" on the PCB).

The datassette port is at the left hand side when viewed from the rear. (Some models have a second datassette port on the right hand side of the computer.)

If you are using a standard IEEE-488 cable with a PET to IEEE adapter, it will be easier to fit the adapter to the cable before fitting the adapter to the PCB edge connector.
Original PET/CBM IEEE-488 cables are "keyed" and can only be inserted one way up.
If you are using one of the adapters shown, make sure that the adapter is connected to the computer the correct way up. Later versions of the adapters are marked to show "This Side Up" when the adapter is installed. Earlier versions of the adapter should be installed so that the "PET<-> IEEE Adapter" text is on the top.

In both cases, the IEEE connector should be below the level of the PCB when fitted.

Images courtesy of RETRO Innovations

The usual method of providing power to petSD+ is to draw power from the datassette port using one of my power cables with data port pass-through.

The power cable should be plugged into the datasette port with the "Computer" and "Datasette" text on the top.


In addition to the Reset push-button, the external model is intended to be fitted with an LCD screen and three additional push-buttons, Previous (S2), Next (S3) and Select (S4), as well as a potentiometer, for adjustment of the LCD contrast. The device also has Red and Green LEDs.

In normal operation, the green LED indicates activity and the red one flashes on errors.

The LEDs have special meaning when petSD+ is powered on or rebooted, at these times, the LEDs are controlled by the boot-loader as described on the Firmware page. In summary, the boot loader turns on the red LED while it is running. If it cannot find a valid application in the chip, it will flash the red LED for two seconds and try to find a valid file once more. During card accesses the green LED is on, during the actual flash operation the green LED flickers rapidly.

The function of the Previous, Next and Select push-buttons is described on this page of the User Guide.




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