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DS91M040 pin-out table vs. diagram inconsistent

Stephen Petlak
Prodigy 60 points

Other Parts Discussed in Thread: DS91M040

The DS91M040 datasheet dated 2013 shows the connection diagram on page 2 and a pin description table on page 3. The table lists pin numbers for the bus signals but the MSB/LSB order is inconsistent with other bus signals in the table, which leads me to wonder if I should trust the diagram or table for correct pin numbers. For example, the bus named "RO" in the table has pin numbers 1, 3, 5, and 7 corresponding to the diagram for RO0 thru RO3, respectively. So the pin number listing (left to right) in the table for this particular bus is LSB to MSB. However, another bus in the table, e.g., "A" shows pins 17, 19, 21, and 23 corresponding to A3 thru A0 (MSB to LSB). Should I assume that the diagram is correct and that the column in the table for pin number doesn't imply bit order for the bus I/O?

  • 0
    TI__Expert 4400 points

    The connection diagram is correct.  The pin number column in the pin descriptions table does not imply bit order.  While the LSB to MSB bit order is indicated by some of the rows (e.g. RO, RE, DE, and DI), this is not consistent for all of the rows.

    The LSB to MSB bit order for the A and B signals is as follows:

         A[0:3] = 23, 21, 19, 17
         B[0:3] = 24, 22, 20, 18

    Gary Melchior