Procedure

Setting the Reference Source

1.Determine the reference period.

A. The reference from which the arm delay is derived is set with bit 0 of the arm control register. The setting of bit 0 (to ’0’ or ’1’) depends on the reference clock and the amount of delay required. Determine the reference from which the delay is derived and set bit 0 accordingly. Retain the settings of bits 7 - 1.

If delay / reference clock period 65,534

bit 0 is set to ’1’ and the maximum delay is 65,534 * reference period

If delay / reference clock period > 65,534

bit 0 is set to ’0’ and the maximum delay is 655,350 * reference period

2.Load the arm delay registers.

A. Write the decimal equivalent of the most significant byte to register 51. Write the decimal equivalent of the least significant byte + 1 to register 53. The additional count (1) is required because there is always a one reference cycle delay from when the digitizer is armed to when it enters the wait-for-trigger state (i.e. is ready to begin sampling).

For example, to program an arm delay of 1 ms:

MSB

LSB

0 1 0 0 1 1 1 0

0 0 1 0 0 0 0 1

7810

3310

7810 is written to register 51

3310 is written to register 53

The reference source from which the sample rate is derived is set with the register listed below.

Reference oscillator register base +4F16

Procedure Write the decimal equivalent bit pattern for the desired reference source to the reference source register (base + 4F16). Retain the settings of bits 7 - 3.

Appendix C

Register Programming 375

Page 375
Image 375
HP E1429A manual Setting the Reference Source