why two separate pins for read and write?

Discussion in 'Embedded Systems and Microcontrollers' started by iitravi, Sep 9, 2012.

  1. iitravi

    Thread Starter New Member

    Sep 2, 2012
    3
    0
    we know microprocessor at a single instant can execute either write instruction or read instruction which can be done by sending a read or write bar signal low or high or vice versa..( if read/write bar=1,perform read function and no write function )how ever in intel family, they have been provided separate pins for these two operations.. why is it so?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,136
    1,786
    They do it because memory chips have separate inputs for Read and Write.

    On devices with RD* and WR* they are both valid stobe signals syncronized with the clock.

    On devices with R/W* and E-Clock you have to combine those two signals to get a valid stobe to the memory device.
    Code ( (Unknown Language)):
    1.  
    2. RDS* = !(R/W* & E-Clock)     ; negative logic read data strobe
    3. WDS* = !(!(R/W*) & E-Clock)  ; negative logic write data strobe
    4.  
    Is that as clear as mud?
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,421
    3,357
    Didn't you already post this question?

    What you see are two different styles of control signals, Intel vs Motorola (now Freescale).
    Intel uses RD' and WR'.
    Motorola uses R/W' and E.
     
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