TDC-GP21 datasheet(53/91 Pages) AMSCO

53 / 91 page

Ultrasonic-Flow-Converter

TDC-GP21

4-8

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complements of 2. Given in multiples of the reference clock.

Time = RES_X * Tref * N, with N = 1, 2 or 4

The measured time interval may not exceed otherwise the ALU will go into overflow and will

write the data ’hFFFFFFFF to the output register.

The configuration of the ALU allows only one hit calculation at the time. In case mor e than

one hit has been measured it is necessary to write new commands to HIT1/HIT2 to

instruct the ALU for calculating the other hits. After writing to HIT1/HIT2 it is necessary

to wait for minimum t.b.d. µs (calibrated data) or t.b.d. ns (un-calibrated data) before

reading or writing again to HIT1/HIT2.

Reading Calibration Raw Data

The calibration data are not addressed directly after the calibration measurement but

after the next regular measurement, before the next INIT.

At the end the TDC-GP21 has to be initialized again to be ready for the next measurement.

This is done by sending the opcode “Init“ so that the TDC accepts new Start and Stop hits.

Source Code Example:

//--------------------------------------------------------------------------

// 1st Measurement plus calibration data readout

gp21_send_1byte(Bus_Type, Init);

// Wait for INT Slot_x

Wait_For_Interrupt(Bus_Type);

// First regular measurement (to readout calibration raw data)

Result = gp21_read_n_bytes(Bus_Type, 4 ,0xB0 ,0x00 ,16);

// readout the new calibration data from result register adr 0x01

gp21_wr_config_reg(Bus_Type, 0x81, 0x67490000);

Diff_Cal2_Cal1 = gp21_read_n_bytes(Bus_Type, 4, 0xB0 ,0x01 ,16);

//--------------------------------------------------------------------------

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TDC-GP21 Datasheet(PDF) 53 Page - ams AG