Nexus
MPC5566 Microcontroller Reference Manual, Rev. 2
25-22 Freescale Semiconductor
25.7.2.3.2 Retrieving Device IDCODE
The Nexus TAP controller does not implement the IDCODE instruction. However, the device
identification message can be output by the NPC through the auxiliary output port or shifted out serially
by accessing the NPC device ID register through the TAP. If the NPC is enabled, transmission of the device
identification message on the auxiliary output port MDO pins occurs immediately after a write to the PCR.
Transmission of the device identification message serially through TDO is achieved by performing a read
of the register contents as described in Section 25.7.2.3.4, “Selecting a Nexus Client Register.”
25.7.2.3.3 Loading NEXUS-ENABLE Instruction
Access to the NPC registers is enabled by loading the NPC NEXUS-ENABLE instruction when NPC has
ownership of the TAP. This instruction is shifted in via the SELECT-IR-SCAN path and loaded in the
UPDATE-IR state. At this point, the Nexus controller state machine, shown in Figure 25-10, transitions to
the REG_SELECT state. The Nexus controller has three states: idle, register select, and data access.
Table 25-15 illustrates the IEEE® 1149.1 sequence to load the NEXUS-ENABLE instruction.
Figure 25-10. NEXUS Controller State Machine
Table 25-15. Loading NEXUS-ENABLE Instruction
Clock TDI TMS IEEE® 1149.1 State Nexus State Description
0 — 0 RUN-TEST/IDLE IDLE IEEE 1149.1-2001 TAP controller in idle state
1 — 1 SELECT-DR-SCAN IDLE Transitional state
2 — 1 SELECT-IR-SCAN IDLE Transitional state
3 — 0 CAPTURE-IR IDLE Internal shifter loaded with current instruction
4 — 0 SHIFT-IR IDLE TDO becomes active, and the IEEE® 1149.1-2001
shifter is ready. Shift in all but the last bit of the
NEXUS_ENABLE instruction.
5–7 0 0 3 TCKS in SHIFT-IR IDLE
8 0 1 EXIT1-IR IDLE Last bit of instruction shifted in
9 — 1 UPDATE-IR IDLE NEXUS-ENABLE loaded into instruction register
10 — 0 RUN-TEST/IDLE REG_SELECT Ready to be read/write Nexus registers
IDLE
NEXUS-ENABLE=1
REG_SELECT
UPDATE-DR=1
DATA_ACCESS
UPDATE-DR=1
NEXUS-ENABLE=1 &&
NEXUS-ENABLE=0
TEST-LOGIC-RESET=1
UPDATE-IR=1
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