4 Replies Latest reply on Jul 6, 2020 5:19 AM by StAd_4731176

    Truth table error on CY62167G?


      HI, I am considering using the CY62167G in a project, but I need some clarification regarding the "Deselect/Power down" function.


      I want to use the part in 2M x8 bit mode.    In this mode,

      * I plan to tie /BYTE to ground

      * and also tie /BHE and /BLE to VSS (datasheet indicates "not used " and "don't care").


      When I look at the truth table on page 16 of the datasheet, the third line looks like an error.  It seems that the /BYTE signal must be "H" to select 1x16M  mode, for the power down mode indicated here.


      Can someone confirm that, for row 3 of the truth table, that /BYTE must be HIGH?



        • 1. Re: Truth table error on CY62167G?

          I will add to this-


          It is not clear in the datasheet how to or not to connect the following signals when /BYTE is connected to VSS:




          I/O8  to I/O14


          Should these signals be grounded?  left No-Connect on the PCB?


          Also, is the same rule applicable to other Cypress SRAMs?  I have read many datasheets from Cypress for TSOP-48 packaged SRAMs and there is no consistent definition for these signals.


          Very confusing!  thanks for any help....

          • 2. Re: Truth table error on CY62167G?

            Please refer following block diagram from the "CY62167G Datasheet Document Number: 001-81537"



            The /BYTE input is used to control the input and output buffers only.

            On other hands the standby control (POWER DOWN CIRCUIT) is controlled by the CE, /BHE, and /BLE inputs.  /BYTE does not affect to the power down mode.


            From this block diagram, /BLE should be asserted (driven to LOW) even if the 2Mx8 configuration is used.




            • 3. Re: Truth table error on CY62167G?

              Hi Stephen,


              For the third row in the truth table the Byte pin need not be high. It can be X (don't care).

              When you are using the SRAM as 2M x 8 configuration, the IO 8 - 14, BLE, BHE  can be left  floating or can be tied GND as per your choice and convenience.


              This is applicable to all SRAM parts in our portfolio. I will also provide your feedback to the BU to append the datasheets.




              • 4. Re: Truth table error on CY62167G?

                Thank you for the reply, Pradipta.

                I guess that by floating /BHE and /BLE, there must be some internal pull down, to ensure that the part doesn't randomly go into low power mode?

                I say this because isn't it possible that with floating /BHE and /BLE, these signals are undefined which I thought for CMOS was a bad idea.  The gates might end up in the HIGH state, which would trigger low power mode.  According to the truth table and the logic diagram, regardless of the other signals on the device, if /BHE and /BLE are both high, then shutdown occurs.


                Anyhow thank you for the confirmation that grounding /BHE and /BLE is acceptable, also same for IO8-IO14.