VXI TECHNOLOGY SVM2608 - Manual (Page 53)

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SVM2608 Programming 53
Write 0x0016E360 @ Base address + 0xC00068
If the Sample Rate register from Example 1 (0x0012C4B0 corresponding to a sample rate of
123 ms) and the Trigger Delay in Example 4 above are set on the SVM2608, the first sample is
taken 1,500,000 x 123 ms = 184,500 seconds (51.25 hours!!!) after the trigger event.
Example 5: Setting Channel 2 and 4 Timeout Register to Timeout after 2.5 s
The Timeout function is designed to prevent the SVM2608 from encountering indefinite time
periods where the module waits for an external trigger event. The clock for the timeout counter is
generated by dividing the reference clock (0.1 µs (10 MHz) for the low-speed Channels 0 – 3 and
8.333 ns (120 MHz) for high-speed channels 4 and 5), generated by an on-board oscillator, by a
preset value determined by bits 15 - 13 of the Timeout register of the respective channel. This is
called the Timeout Base Clock (or TOSEL). Bits 12 - 0 in the TIMEOUT register load a counter
(Timeout Counter) that determines the number of Timeout Base Clocks after which the timeout
flag is set.
To determine the minimum Timeout Base Clock for Channel 2, divide the desired Timeout value
by the maximum value allowed in the Timeout Counter register and round it up to the next highest
value available:
TIMEOUT BASE CLOCK ≥ TIMEOUT VALUE / (2
13 -1) = 2.5 s / 8191 ≈ 0.305 ms
The nearest Timeout Base Clock available, which is greater than or equal to 0.305 ms, is 1 ms. Set
the TOSEL bits in the Timeout register to ‘010’.
To determine the value for the Timeout Counter, divide the desired Timeout value by the Timeout
Base Clock:
TIMEOUT COUNTER = TIMEOUT / TIMEOUT BASE CLOCK
= 2.5 s / 1 ms
= 2.5 s / 10 -3 s
= 2,500
The value that needs to be programmed in the Timeout Counter is 2,500 = 0x9C4
The value which needs to be programmed into the Timeout register is determined by multiplying
the Timeout Base by 2
13 and adding it to the Timeout Counter value:
TIMEOUT REGISTER = TIMEOUT BASE * 2
13 + TIMEOUT COUNTER
= 2 * 8192 + 2500
= 18884
= 0x49C4
To program the Timeout value for Channel 2, write 0x49C4 at address 0xC00044.
The Timeout Counter starts counting down from the value it is loaded with after the channel is
Armed, all the Pre-Trigger samples (if any were specified) are acquired and the Delay Points (if
any were specified) are acquired. It stops counting as soon as either a trigger event occurs or when
it reaches zero. Terminating (aborting) the acquisition by resetting the ARM bit also stops the
Timeout counter.
If the Timeout Counter reaches zero, the Timeout Occurred flag is asserted.