MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
25-21
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
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
, transitions to
the REG_SELECT state. The Nexus controller has three states: idle, register select, and data access.
illustrates the IEEE
1149.1 sequence to load the NEXUS-ENABLE instruction.
Figure 25-9. 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
Summary of Contents for MPC5553
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