Virtex-4 BSCAN

The Virtex-4 data sheet states that the BSCAN module can support 4 user-data registers.

However there is an Errata sheet which states that early (ES) parts only supported one register.

The "Virtex-4 Libraries Guide for HDL Designs" shows a BSCAN_VIRTEX4 element supporting only one user register (although it mentions USER1 & USER2 instructions, suggesting two registers).

The library unisim_VCOMP.vhd shows:

component BSCAN_VIRTEX -- This drives two user registers port ( DRCK1 : out std_ulogic := 'H'; DRCK2 : out std_ulogic := 'H'; RESET : out std_ulogic := 'H'; SEL1 : out std_ulogic := 'L'; SEL2 : out std_ulogic := 'L'; SHIFT : out std_ulogic := 'L'; TDI : out std_ulogic := 'L'; UPDATE : out std_ulogic := 'L'; TDO1 : in std_ulogic := 'X'; TDO2 : in std_ulogic := 'X' ); end component;

component BSCAN_VIRTEX4 -- This drives one user register generic ( JTAG_CHAIN : integer := 1 ); port ( CAPTURE : out std_ulogic := 'H'; DRCK : out std_ulogic := 'H'; RESET : out std_ulogic := 'H'; SEL : out std_ulogic := 'L'; SHIFT : out std_ulogic := 'L'; TDI : out std_ulogic := 'L'; UPDATE : out std_ulogic := 'L'; TDO : in std_ulogic := 'X' ); end component;

So I am confused :) Can anyone tell me just how many JTAG user registers V4 does support?

Reply to
David R Brooks
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David R Brooks schrieb:

there are 4 but the way of using them is different then other families if for others there was one BSCAN primitive that allowed access to two user instructions, then V4 has

1 primitive where

chain number selects which USERx instruction the bscan is linked to

so to access all 4 USERx you instantiate 4 times the same prim with different generic for chain num

now as of some V4-ES, only chain 1 is useable, others dont work so they are probably there but can not be used.

notice that on some V4-ES RESET output of the BSCAN has wrong polarity that also may need special handling.

the 1 chain only issue caused most problems with MDM in the v4-lx25es where defautl MDM was using non-working chain 2, so there was special workaround to set MDM ip to use chain 1 and have matching XMD also

Antti

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Reply to
Antti

Many thanks!

Reply to
David R Brooks

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