QProbe contains two programmable CPLD logic chips.
These are multifunction:
- they drive most of the LEDs
- they demultiplex QBUS DAL signals onto ADDRESS and DATA LEDs,
- also QBUS IRQ and DMA signal pulses are elongated from micro seconds to several 100 milliseconds to become visible.
- several "operation modes" set via DIP switch aid in self test or special diagnostic challenges.
The whole CPLD logic consists of several components;
- 2x CPLDs Intel EPM240T100
- 3.3V voltage regulator
- voltage convertering buffers, to scale QBUS 5V downto 3.3.V
- 4 DIP switches to setup operation modes
- 22 freely programmable signals, normally used to route the demultiplexed QBUS ADDRess to a logic analyzer ports. Despite labeled "ADDR" on the PCB, they may have different meanings when modified code is loaded into the CPLDs.
- a JTAG header to reprogram the CPLDS with help of "Altera USB-Blaster" adapter and Intel "QUARTUS" development suite.
Some LEDs are not driven by CPLDs, but are connected directly to QBUs signals
+5V, +12V, POK, DCOK, EVNT, BS7, DIN, DOUT, REF, WTBT, SYNC, RPLY.