Front Panel Data Port

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The front panel data port (FPDP) is a bus that provides high speed data transfer between two or more VMEbus boards at up to 160 MB/sec with low latency. The FPDP bus uses a 32-bit parallel synchronous bus wired with an 80-conductor ribbon cable.[1]

The following interface functions are supported:[2]

  • FPDP/TM (transmitter master) - drives data and timing signals onto the FPDP, and also terminates the bus signals at one end of the ribbon cable
  • FPDP/RM (receiver master) - receives data from the FPDP synchronously with the timing signals provided by the FPDP/TM, and also terminates the bus at the opposite end of the cable to the FPDP/TM
  • FPDP/R (receiver) - receives data form the FPDP synchronously with the timing signals provided by the FPDP/TM; it does not terminate the bus. More than one FPDP/R can be connected to the FPDP bus. It can also be an alternate function to that of FPDP/RM via software control.

The connector, denoted by the FPDP specification, is a KEL P/N 8825E-080-175.

Interface signals[edit]

  • D<31:0> : Data bus driven by FPDP/TM
  • DIR_n  : Active low Direction signal driven by FPDP/TM
  • DVALID_n: Active low data valid indication driven by FPDP/TM
  • STROBE  : A free running clock supplied by FPDP/TM
  • NRDY_n  : Active low not ready signal driven by FPDP/R or FPDP/RM. Asserted before the commencement of transfer of data by the FPDP/R or FPDP/RM asynchronous to STROBE.
  • PSTROBE : Optional Differential PECL version of the STROBE driven by FPDP/TM
  • SUSPEND_n : Active low suspend signal asserted by FPDP/R or FPDP/RM asynchronous to STROBE to inform the transmitter that buffer flow condition may occur. The transmitter may delay not more than 16 clocks before it suspends the data transfer.
  • SYNC_n  : Active low synchronization pulse provided by FPDP/TM.
  • PIO1, PIO2 : Programmable I/O lines for user purposes

Data frames[edit]

The following types of data frames are supported:

  • Unframed Data
  • single frame Data
  • Fixed size Repeating Frame Data
  • Dynamic Size Repeating Frame Data

Cable length[edit]

FPDP interfaces work with up to a cable length of 1 meter when used in multi-drop configuration. They work up to 2 meter when using STROBE signal during point-to-point configuration. They work up to 5 meter when used with PSTROBE differential signal during point-to-point configuration.

See also[edit]

  • VMEbus - a computer bus standard widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987
  • Serial FPDP - High-speed serial version of FPDP, that can be sent short distances over copper cables, or longer distances over optical fiber cable.


  1. ^ Standard VITA 17-199x, VMEbus International Trade Association (VITA),
  2. ^