MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
25-22
Freescale Semiconductor
25.7.2.3.4
Selecting a Nexus Client Register
When the NEXUS-ENABLE instruction is decoded by the TAP controller, the input port allows
development tool access to all Nexus registers. Each register has a 7-bit address index.
All register access is performed via the SELECT-DR-SCAN path of the IEEE
1149.1–2001 TAP
controller state machine. The Nexus controller defaults to the REG_SELECT state when enabled.
Accessing a register requires two passes through the SELECT-DR-SCAN path: one pass to select the
register and the second pass to read/write the register.
The first pass through the SELECT-DR-SCAN path is used to enter an 8-bit Nexus command consisting
of a read/write control bit in the lsb followed by a 7-bit register address index, as illustrated in
. The read/write control bit is set to 1 for writes and 0 for reads.
The second pass through the SELECT-DR-SCAN path is used to read or write the register data by shifting
in the data (lsb first) during the SHIFT-DR state. When reading a register, the register value is loaded into
the IEEE
1149.1-2001 shifter during the CAPTURE-DR state. When writing a register, the value is
loaded from the IEEE
1149.1-2001 shifter to the register during the UPDATE-DR state. When reading
a register, there is no requirement to shift out the entire register contents. Shifting may be terminated after
the required number of bits have been acquired.
illustrates a sequence that writes a 32-bit value to a register.
msb
lsb
7-bit register index
R/W
Figure 25-10. IEEE
1149.1 Controller Command Input
Table 25-16. Write to a 32-Bit Nexus Client Register
Clock
TMS
IEEE 1149.1 State
Nexus State
Description
0
0
RUN-TEST/IDLE
REG_SELECT
IEEE 1149.1-2001 TAP controller in idle state
1
1
SELECT-DR-SCAN
REG_SELECT
First pass through SELECT-DR-SCAN path
2
0
CAPTURE-DR
REG_SELECT
Internal shifter loaded with current value of controller
command input.
3
0
SHIFT-DR
REG_SELECT
TDO becomes active, and write bit and 6 bits of
register index shifted in.
7 TCKs
11
1
EXIT1-DR
REG_SELECT
Last bit of register index shifted into TDI
12
1
UPDATE-DR
REG_SELECT
Controller decodes and selects register
13
1
SELECT-DR-SCAN
DATA_ACCESS
Second pass through SELECT-DR-SCAN path
14
0
CAPTURE-DR
DATA_ACCESS
Internal shifter loaded with current value of register
15
0
SHIFT-DR
DATA_ACCESS
TDO becomes active, and outputs current value of
register while new value is shifted in through TDI
31 TCKs
47
1
EXIT1-DR
DATA_ACCESS
Last bit of current value shifted out TDO. Last bit of
new value shifted in TDI.
48
1
UPDATE-DR
DATA_ACCESS
Value written to register
49
0
RUN-TEST/IDLE
REG_SELECT
Controller returned to idle state. It could also return
to SELECT-DR-SCAN to write another register.
Summary of Contents for MPC5553
Page 5: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 2 Freescale Semiconductor...
Page 21: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 xvi Freescale Semiconductor...
Page 47: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 1 26 Freescale Semiconductor...
Page 163: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 4 20 Freescale Semiconductor...
Page 179: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 5 16 Freescale Semiconductor...
Page 561: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 13 38 Freescale Semiconductor...
Page 615: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 14 54 Freescale Semiconductor...
Page 707: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 17 68 Freescale Semiconductor...
Page 755: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 18 48 Freescale Semiconductor...
Page 873: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 19 118 Freescale Semiconductor...
Page 984: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 Freescale Semiconductor 21 41...
Page 985: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 21 42 Freescale Semiconductor...
Page 1019: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 22 34 Freescale Semiconductor...
Page 1129: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 25 90 Freescale Semiconductor...