TDC-GPX datasheet(25/54 Pages) AMSCO

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TDC-GPX

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2.3 I-Mode Basics

In this mode TDC-GPX offers

8 stop channels referring to 1 start channel,

Each of typ. 81 ps resolution

5.5 ns pulse-pair resolution

Start-retrigger up to 7 MHz

Unlimited measuring range with internal start re-

trigger

All inputs of LVTTL type

Selectable rising/falling edge sensitivity for all

channels

Several disable possibilities for all channels

Start

Stop

Figure 18: Measurement timings

**with StopDisStart = 1

Input circuitry

The detailed input structure is shown in Figure 17:

Input circuitry. Each input separately can be set to be

sensitive to rising or falling edge. This is done in regis-

ter0, TRiseEn[8…0] and TFallEn[8…0]. The LSB stands

for the TStart input, the MSB TStop8 input. A zero in

the channel bit for TRiseEn and TfallEn at the same

time disables the channel.

All inputs can be disabled by hardware, the stop inputs

in pairs (pin ‘StopDis1’ disables inputs TStop1 and

TStop2, etc.). They also can be disabled by Software

setting the ‘Disable’ bits in register 2. The TDC-GPX

offers the possibility to disable the Stop inputs auto-

matically until a Start is coming in. This is set by Stop-

DisStart = ‘1’ in register 5.

S tar t Retr igger

After an initial start event, the TDC-GPX can generate

its own internal starts. This is controlled by the pa-

rameter “StartTimer” in register 4. The start retrigger

rate may not exceed 7 MHz.

Single Start

StartTimer = 0 switches off the internal Start genera-

tion. In this mode the measuring range is limited to 2

BIN

≈ 10.6 µs (@ BIN = 81 ps). Further pulses at

TStart will be ignored.

Internal Start Retrigger

The period of the start repetition is programmable in

multiples of the 40 MHz reference clock between

(4+1) and (255+1) x 25ns (Register 4: Start-

Timer[7…0]).

The time interval between the initial, external start and

the first internal one will vary. It is therefore measured

and stored as ‘Start01’ in register 10. It can be read

out from this register as a 17 Bit integer in multiples

of BIN.

The time intervals between following starts are fixed

and referred to as (N +1) x Tref. Additionally, there is

an 8 Bit counter for the start number (Start#). The

start number is added to the output data.

A further option is to feed the highest bit of the Start

counter to the IrFlag output pin by setting register 11,

Bit 26 Start#U to one. With this signal the intenal

start number counter can externally be extended to

any size.

The internal start retrigger allows an unlimited

measuring range for the TDC-GPX.

External Start Retrigger

A further option is to retrigger the Start externally.

This option is activated by setting StartTimer = 1 (Reg

4) and StartRetrig = 1 (Reg 5). The further behavior is

the same as for the internal start retrigger. The

maximum retrigger frequency is typically 7 MHz. The

time interval between two Starts is measured and

stored in the “Start01” register. This value is reason-

able only if the delay between two Start pulses does

not exceed the measuring range of 2

17 BIN

≈ 10.6 µs.

Figure 19

Par.

Time (Condition)

Min.

Max.

Description

tph

1.5 ns

Positive pulse width

tpl

1.5 ns

Negative pulse width

tss

0 ns min

**5.2 ns

9.4 µs

*unlimited

Start to Stop

trr,

tff

5.5 ns typ.

6.9 ns max.

edge to edge

# @ 87 ps resolution

*with int. start retrigger

Asynchronous

Start

Start# 1

Start# 2

Start# 3

time

Start01

measured

(N+1) * 25ns

fixed

(N+1) * 25ns

fixed

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