Tool/software: Starterware
SPI FOR TRF7961
hello EXPERT,
I have the question to confirm with you on SPI OF TRF7961,now I attach one ppt to show detail information,please answer me based on it;TRF7961.zip
thanks a lot.
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Tool/software: Starterware
SPI FOR TRF7961
hello EXPERT,
I have the question to confirm with you on SPI OF TRF7961,now I attach one ppt to show detail information,please answer me based on it;TRF7961.zip
thanks a lot.
Hello Mike,
I am going to assume that the MISO line is also shared even though not indicated in your PPT.
1) Yes
2) TI Recommendation is to use tri-states for MISO, MOSI, and SCLK. It may be possible to only do MISO if the TRF7961 is DISABLED by pulling EN=LOW during other SPI transactions, but there is no precedent for doing. Again, recommendation is Tri-state buffer on each of MISO, MOSI, and SCLK.
3) Yes this is specific to the TRF7961. It is due to the chip design.
4) I did not make this decision, my best guess is it is not considered a specification and thus not included in the DS.
5) We do not characterize the likelihood of such behavior. We simply are explaining the device behavior so you understand the risks. If you choose to ignore TI recommendations, then it is up to you validate your products functionality and take the RISK that your product may malfunction at some point.
hello Ralph,
add one information:MISO line is only used to TRF7961,not shared to other device.
is there any difference?
thanks.
Hello Mike,
If MISO is not shared with other devices, then I don't see any need for a tri-state buffer on it. As far as MOSI/SCLK go, I stand by what I said in the answer to question 2 above which I will reword for clarity:
2) TI Recommendation is to use tri-state's for MISO, MOSI, and SCLK. It may be possible to not apply tri-state's to MOSI/SCLK if the TRF7961 is DISABLED by pulling EN=LOW during other SPI transactions, but there is no precedent for doing. Again, recommendation is Tri-state buffer on MOSI and SCLK.
hello Ralph,
can you tell me what's negative impact when the tri-state buffer is not used? Does it impact RFID controller itself, for example, does it impact RFID communication between controller and RFID tag?
or it will impact other device in the same SPI bus?
thanks.