VT4 info

VME-VT4 - 4-channel timestamp module using the VME-IO32 board

UPDATE: July 2018 - some changes were made to operation ...
Time starts at first cycle pulse after reset, and then runs continuously
Gates are counted and written in place of cycle counter on gate-rise/fall
Gate-count resets to zero at start of each new cycle

VME interface

VME A32/D32 access only. Rotary switches SW1, SW2 and SW3 set the upper 12 bits of the address. VME registers are listed in the table below.

Registers

Number	Address	Name	Access	Description
0	0x0003C	CSR	RW	Control/Status Register
1	0x00040	Test	RW	Test Register
2	0x00044	Tstamp	R	Firmware Timestamp
3	0x00048	Nwords	R	Data Words available
4	0x0004C	Data_Low	R	Data lower half [bits 31:0]
5	0x00050	Data_Hi	R	Data upper half [bits 63:32] *and select nextword*

CSR Register (0x00000)

The first 8 bits auto-clear after a few clocks, bits 8, 9 indicate databuffer empty/full the other bits are currently unused and retain whatever is written to them

CSR Description

Bit	Name	Access	description
0	Reset	W	autocleared to zero
1-7	unused	W	autocleared to zero
8	Empty	R	Data Buffer Empty
9	Full	R	Data Buffer Full
10-31	unused	R/W	unused

reset bit: Writing 1 here resets the module to powerup state.

Operation

inputs 1 to 6 are used

inputs 1-4 are tdc inputs input 6 is tdc-gate input 5 is "new-cycle"

at start of run, the module should be reset

cycles are counted, timestamps reset on first tdc-gate of each cycle tdc inputs are only counted during tdc-gates (tdc-gates are not counted)

data words are written to buffer on each: cycle, tdc-gate-rise, tdc-gate-fall, tdc-input[if gate high]

data words are all 64bits with same format (from msb to lsb) ...

  [6bit id, 10bit cycle-count, 48bit timestamp]

6 id bits are cycle,gaterise,ch1-4 [tdc-gate-fall words will have no id bits set]

as the module is set up currently, if inputs/cycle/tdc-gate occur simultaneously, only one data word will be produced, but it will have all relevant id bits set.

Read data low half first, then upper half, as reading upper half moves to next word in buffer.