TDC-GP2 acam messelectronic gmbh, TDC-GP2 Datasheet - Page 19

• Manufacturer Part Number: TDC-GP2
• Description: Precision Time Interval Measurement
• Manufacturer: acam messelectronic gmbh

3.2 Measurement Flow
Figure 7
3.2.1 Configuration
At the beginning the TDC-GP2 has to be configured. The
main settings for measurement range 1 are:
a. Select measurement range1 setting register 0,
Bit3, MRange2 = 0.
b. Select the reference clock (see also section 5.1)
Register 0, Bits 10&11, START_CLKHS defines the
switch-on behavior of the high-speed clock. If only the
32kHz is used this is be set to "0". If only the high-
speed clock is used this is be set to "1"(continuously
on). In case both oscillators are used for current saving
reasons this should be set to "2" for ceramic
oscillators and to "3" for quartz oscillators".
Register 0, Bits 12&13, ClkHSDiv sets an additional
internal divider for the reference clock (1,2 or 4). This
is important for calibrated measurements in
measurement range 1 because the ALU works
correctly only if 2*Tref(intern) is bigger than the
maximum time interval to be measured. Otherwise the
ALU output is 0xFFFFFFFF.
Make also sure that 2*Tref(intern) < 1.8 µs to avoid a
timeout during calibration.
c. Set the number of expected hits
In register 1, Bits 8 to 10 and 11 to 13, HITIN1 and
HITIN2 the user has to define the number of hits the
TDC-GP2 has to wait for. A maximum of 4 on each
Configuration
-Mode
-How many hits per Chan.
-Clock
-Calibration
TDC unit waits for
-Start pulse
-Stop pulse(s)
ALU postprocessing
according to
HIT1&HIT2
Calibration
measurement
Initialization
Interrupt
acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
3.2.2
3.2.3
timeout
3.2.1
3.2.1
3.2.2
3.2.3
one stop
only
Read Data
Read Data 3.2.4
Write
new value into
HIT1 & HIT2
more than
one stop
3.2.4
3.2.4
19
channel is possible. The TDC-GP2 measures until the
set number of hits is registered or a timeout occurs.
d. Select calibration
As the BIN size varies with temperature and voltage the
TDC-GP2 ALU can internally calibrate the results. This
option is switched on by setting register 0, Bit5,
Calibrate = "1". It is recommended to do this.
For the calibration the TDC measures 1 and 2 cycles of
the reference clock. The two data are stored as Cal1
and Cal2.
There are two ways to update the calibration data Cal1
and Cal2:
- Separate calibration by sending opcode
Start_Cal_TDC via the SPI interface
- Automatic update by setting register 0, Bit 4,
DisAutoCal = "0". In most applications this will be the
preferred setting.
e. Define ALU data processing
While the TDC unit can measure up to 4 hits on each
channel the user is free in his definition what the ALU
shall calculate. The settings are done in register 1, Bits
16 to 19 and 20 to 23, HIT1 and HIT2. Both
parameters can be set to:
0 = Start
1 = 1. Stop Ch1
2 = 2. Stop Ch1
3 = 3. Stop Ch1
4 = 4. Stop Ch1
6 = Cal1 Ch1
7 = Cal2 Ch1
The ALU calculates Hit1 - Hit2.
Examples:
Reg1 = 0x01xxxx
Reg1 = 0x2Bxxxx
Reg1 = 0x06xxxx
In case calibration is active the ALU does the full
calibration calculation (except when reading the
calibration values. In this case the ALU writes the
Cal1/Cal2 raw data to the output register).
N = 1, 2 or 4.
RES
Cal
Time
2
_
X
Cal
RES
1
HIT
Cal
_
gradient
X
1
2
T
HIT
Cal
ref
2
1
1
3
Cal1
2
s t
r d
ClkHSDiv
Stop Ch1-Start
Stop Ch2-2
3.2 Measurement Flow
RES
9 = 1. Stop Ch2
A = 2. Stop Ch2
B = 3. Stop Ch2
C = 4. Stop Ch2
TDC-GP2
_
n d
X
Stop Ch1
T
ref
N