BitScope "Spock" PLD

The original BitScope used a Lattice PLSI1016 PLD to implement the capture engine.

We call it Spock and it "soaks up" a lot of logic and makes the circuit look much simpler than it really is. It implements the equivalent of 16 to 20 medium density TTL devices.

Spock Chip.

Spock performs two functions:

(1) Address generation for the SRAM capture buffers, and

(2) 8 bit pattern matching for trigger generation.

It is driven by the zz-clk signal and operates in one of two modes:

COUNT mode (RB4 low): counter enabled and comparator monitoring the byte stream for trigger matches.

SHIFT mode (RB4 high): counter shifting in bits from A-DATA (RB0), and shifting out bits to SEL0 (RB1). We can reload the counter and find out where it was up to when we stopped it. Bits from the top of the counter are also shifted up to the comparator circuits to load the trigger.

Spock is connected to the three internal busses in BitScope:

BUS Name Description

A13/A0 Address The 14 bit address bus. Spock drives this bus when capturing data.

DD7/DD0 Digital Data Data from the Logic POD is read into Spock during a capture trace for use by the trigger logic inside Spock.

AD7/AD0 Analog Data Data from the A/D convertor is read into Spock during a capture trace for use by the trigger logic inside Spock.

Full details of Spock's functional operation are available here.