THS 788 问题 (英文)
We use in one of our product the THS 788 chip (from TI) and we are encountering some trouble with it.
In our setup we connect to Sync Input A and EventA two periodic signals slightly delayed by 1 ns.
Then we vary their common frequency.
We observe the following behavior when reading the internal ChannelA result register:
- The results are correct when the common frequency is lower than 8MHz. (we can read a correct delay of 1 ns)
- For frequencies between 9MHz to 25MHz, we observe 3 different values of the delay (1 ns, 1ns + period of signal, 1 ns - period)
- For higher frequencies (60MHz to 80MHz) we observe many values, which seem related by multiple of the signal period. (1 ns - 27 period, 1 ns - 28 period. etc.)
Could you have additional information regarding this behavior.
- The manual mentions negative timestamps when start occurs just after a stop but can the delays be larger than the time window between two starts ?
In addition we are using the high speed serial interface to read data from our FPGA which is configured in 8 bit mode.
- The documentation mentions the last bit as the sign bit which we do not observe. Do we have a way to program it as it or are we doing something wrong ?
The THS788 is configured as follow: (non specified registers are set their initial values)
- Control register values:
- 0x80 -> 0xA600
- RCLK_EN = '1', Result Clock Enabled
- Sync_IP_En = '1', Enables the sync channel
- OT_En = '1', Enables the overtemperature alarm circuits
- RCLK_Sel = "10", Result-Interface Clock = 300MHz
- RLenght = "000" -> Result transfer format = 8 bits
- Control register values:
- 0x81 -> 0x0002
- CHA_IP_EN= "1",
- EN_CHA = "1"
- DDR 0x00 CHA Control Register -> DATA 0x0003 -> CHA_IP_EN(1), EN_CHA(1
- 0x00 -> 0x0003
- CHA_IP_EN = "1",
- EN_CHA = "1"
About THS788, I can't find documents for THS788. May be you could attach the datasheet and we could discuss for your question.
In addition, we could communicate with Chinese directly in order to understand your question completely.
Thanks so much for the feedabck. Attachment is the datasheet. Sorry it is in English because we are joint venture company and the engineer in charge of teh design is foreigner. It is used in the photon detector which is very sensitive for the timing
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