View source for VT4 info

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

=== 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 ====
{| cellpadding="10" cellspacing="0" border="1"
! 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

{| cellpadding="10" cellspacing="0" border="1"
|+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.