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Table 10: USER1 and USER2 Instruction Values

Binary PatternInstruction

00 0000 1100USER0

00 0000 1110USER1

The USER1 instruction targets the virtual IR of either the sld_hub or a SLD node. That is, when the USER1

instruction is issued to the device, the subsequent DR scans target a specific virtual IR chain based on an

address field contained within the DR scan. The table below shows how the virtual IR, the DR target of the

USER1 instruction is interpreted.

The VIR_VALUE in the table below is the virtual IR value for the target SLD node. The width of this field is m

bits in length, where m is the length of the largest VIR for all of the SLD nodes in the design. All SLD nodes

with VIR lengths of fewer than m bits must pad VIR_VALUE with zeros up to a length of m.

Table 11: USER1 DR

– 1

VIR_VALUE [(m – 1)..0]ADDR [(n – 1)..0]

The ADDR bits act as address values to signal the active SLD node that the virtual IR shift targets. ADDR is n

bits in length, where n bits must be long enough to encode all SLD nodes within the design, as shown below.

n = CEIL(log

(Number of SLD_nodes +1))

The SLD hub is always 0 in the address map, as shown below.

ADDR[(n -1)..0] = 0

Discovery and enumeration of the SLD instances within a design requires interrogation of the sld_hub to

determine the dimensions of the USER1 DR (m and n) and associating each SLD instance, specifically the

Virtual JTAG megafunction instances, with an address value contained within the ADDR bits of the USER1

DR.

The discovery and enumeration process consists of the following steps:

1. Interrogate the SLD hub with the HUB_INFO instruction.

2. Shift out the 32-bit HUB IP Configuration Register to determine the number of SLD nodes in the design

and the dimensions of the USER1 DR.

3. Associate the Virtual JTAG instance index to an ADDR value by shifting out the 32-bit SLD node info

Issuing the HUB_INFO Instruction

The SLD hub contains the HUB IP Configuration Register and SLD_NODE_INFO register for each SLD node

in the design. The HUB IP configuration register provides information needed to determine the dimensions

of the USER1 DR chain.

Virtual JTAG Megafunction (sld_virtual_jtag)

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Issuing the HUB_INFO Instruction

2014.03.19

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Altera Virtual JTAG IP Core Manual de usuario Pagina 30