Answers Database

xc4000E/EX/XL and 5200: Difference between the preamble/length count of XC4000/E/EX and the XC5200


Record #2017

Product Family:  Hardware

Product Line:  5200

Problem Title:
xc4000E/EX/XL and 5200: Difference between the preamble/length count of
XC4000/E/EX and the XC5200



Problem Description:
What is the difference between the XC4000/E/EX length count
and the XC5200 length count?


Solution 1:

The configuration data for XC4000/E/EX devices consist of a
composite 40-bit preamble/length count.  The configuration
data for XC5200 devices consist of a composite 48-bit pream-
ble/length count.  Why is this the case?

for 4k:
-------

Fill Byte:	 11111111b   = FFh =>	 8 bits
Preamble Code:	 0010b	     =	2h =>	 4 bits
Length Counter:  COUNT(23:0)	   =>	24 bits
Fill Byte:	 1111b	     =	Fh =>+)  4 bits
				     ----------
	  Total preamble/length count = 40 bits

Therefore the .BIT file will have a preamble/length count
of:

		      FF20h

and the PROM file will have a preamble/length count of:

		      FF04h

* Note:  In the XC4000EX family of devices, this applies to
	 all configuration modes, except Express Mode.	4k
	 Express Mode does not have a length count.

for 5k:
-------

Fill Byte:	 11111111b   = FFh =>	 8 bits
Preamble Code:	 11110010b   = F2h =>	 8 bits
Length Counter:  COUNT(23:0)	   =>	24 bits
Fill Byte:	 11111111b   = FFh =>+)  8 bits
				     ----------
	  Total preamble/length count = 48 bits

Therefore, the .BIT file will have a preamble/length count
of:

		       FFF2h

and the PROM file will have a preamble/length count of:

		       FF4Fh

The additional 8 bits in the 5k preamble/length count comes
from an additional 'F' prior to '4', and an additional 'F'
after the length count.

* Note:  This also applies to 5k Express Mode, which does
	 have a length count.



End of Record #2017