Pico Systems

CAMAC Time Stamp

The Pico Systems Time Stamp module contains a 48-bit counter which runs at a 10 MHz clock rate. So each count represents a time interval of 100 nS. The time count is converted to Gray code so that it can be asynchronously sampled without incorrect values being recorded. After a 48-bit latch stores the Gray code value, it is converted back to binary information, which can be read out as either 3 16-bit words or 2 24-bit words. The time value can also be loaded as either 3 16-bit words or 2 24-bit words. The clock can be started and stopped by CAMAC commands or external signals, and the external clock run signal can be disabled from the CAMAC port. The 48-bit latch can also be triggered by either CAMAC commands or external inputs. The two external inputs are NIM-negative signals on Lemo connectors. These inputs both have 50 Ohm termination resistors. The module occupies 1 slot in a standard CAMAC crate.

Front Panel Controls:

Run Clock - Lemo Connector

The Run Clock input will cause the clock to run as long as this signal is pulled to a NIM-negative active level, ie. a voltage lower than -.8 Volts (provided that the CAMAC clock disable bit is not set in the command register).

Latch - Lemo Connector

The Latch input will cause the clock count to be sampled at the leading edge when it is taken to a NIM-negative active level.

Load Fail - Red LED

This light will blink for slightly less than one second when the CAMAC crate is powered on, and should not light at any other time. The blink ocurrs when the FPGA program is loaded from a serial PROM, and should go out when the program has been correctly loaded. If it stays lit, it indicates the program did not load correctly into the FPGA. The module will not function in that state.

Clock Running - Green LED

This light indicates that the clock is running.

N - Yellow LED

The N light indicates that the CAMAC bus has given the module a command.

CAMAC commands:

F16 A0 Write Command Register

F0 A0 Read Command Register

  • Bit 0 - Run Clock
  • Bit 1 - Trigger Latch
  • Bit 2 - Disable External Run Clock input
  • Bit 3 - Reset Clock to zero

    F16 A1 Write Clock bits 15-0 (16 bits)

    F16 A2 Write Clock bits 31-16 (16 bits)

    F16 A3 Write Clock bits 47-32 (16 bits)

    F16 A4 Write Clock bits 23-0 (24 bits)

    F16 A5 Write Clock bits 47-24 (24 bits)

    F0 A1 Read Clock bits 23-0 (16 OR 24 bits)

    F0 A2 Read Clock bits 31-16 (16 bits)

    F0 A3 Read Clock bits 47-32 (16 bits)

    F0 A4 Read Clock bits 47-24 (24 bits)

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