Altera Virtual JTAG IP Core - Manual (Page 30)

Table 10: USER1 and USER2 Instruction Values
Binary Pattern Instruction
00 0000 1100 USER0
00 0000 1110 USER1
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
0 m – 1 m m + n – 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
2
(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
register for each SLD node in the design.
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) Altera Corporation
Send Feedback
UG-SLDVRTL
Issuing the HUB_INFO Instruction 30
2014.03.19