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Bit 31 30 28 27 24 23 0
TDI
Write Enable /
Write Failure
Block Select Register Number Register Value
TDO
Access RW W W RW
Bit 7 6 4 3 0
TDI
Write Reserved ConnectKey
TDO
Access W R RW
Reset 0 0 b0110
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5.3.2.8 Connect Register
This register guards the device from noise, hot connection of an emulator cable, or accidental scan by a
misconfigured scan controller. This register reduces the chances of accidentally engaging debug functions
due to noise or accidental scans. Refer to Figure 5-10 and Table 5-11 for more details.
Figure 5-10. Connect Register
Table 5-11. Connect Register
Bit Field Width Type Reset Description
Must be 1 to write the Connect Key. A value of 0 is a read.
7 Write Enable 1 W 0
When read, a value of 0 is returned.
6-4 Reserved 3 R 0 Reserved
When this field holds the key-code of 1001, the scan
controller is considered to be connected. All other values are
3-0 ConnectKey 4 RW 0110
the not-connected state. In this state, only a limited number
of IR instructions are valid.
5.3.3 ROUTER Scan Chain
This register accesses all TAP linking and control registers. The scan chain is 32 bits long. Refer to
Table 5-12 for more information.
Figure 5-11. ROUTER DR Scan Chain
402
JTAG Interface SWCU117A–February 2015–Revised March 2015
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