Table 513. Loading Nexus-Enable Instruction - STMicroelectronics SPC572L series Reference Manual

GTM Development Interface (GTMDI)
42.6.5.2 Loading NEXUS-ENABLE instruction
Access to the GTMDI registers is enabled when the TAP controller instruction register is
loaded with the NEXUS-ENABLE instruction. The current instruction value is loaded into the
IEEE 1149.1 shifter in the CAPTURE-IR state. The 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
the IEEE 1149.1 sequence to load the NEXUS-ENABLE instruction.
TEST-LOGIC-RESET=1
Clock TMS IEEE 1149.1 State
0 0 RUN-TEST/IDLE
1 1 SELECT-DR-SCAN
2 1 SELECT-IR-SCAN
3 0 CAPTURE-IR
4 0 SHIFT-IR
12 1 EXIT1-IR
13 1 UPDATE-IR
14 0 RUN-TEST/IDLE
42.6.5.3 Selecting an IEEE 1149.1 register
When the NEXUS-ENABLE instruction is loaded in the GTMDI TAP controller instruction
register, the input port allows development tool access to all GTMDI registers. Each register
has a 7-bit address index. Some clients have registers with the same index as registers in
other clients. Therefore, to access the registers of a particular client, the Client Select
Control register must be set for that client.
952/2058
Figure 456, transitions to the REG_SELECT state.
Figure 456. Nexus controller state machine
NEXUS-ENABLE=1 &&
UPDATE-IR=1

Table 513. Loading NEXUS-ENABLE instruction

Nexus state
IDLE
IDLE
IDLE
IDLE
IDLE
4 TCKs
IDLE
IDLE
REG_SELECT NEXUS-ENABLE ready to be read
DocID027809 Rev 4
NEXUS-ENABLE=0
IDLE
NEXUS-ENABLE=1
REG_SELECT
UPDATE-DR=1
DATA_ACCESS
IEEE 1149.1 controller in idle state
Transitional state
Transitional state
Internal shifter loaded with current instruction
TDO becomes active, and the IEEE 1149.1 shifter is
ready. Shift in all but the last bit of the NEXUS_ENABLE
instruction
Last bit of instruction shifted in
NEXUS-ENABLE loaded into instruction register
Table 513
UPDATE-DR=1
Description
RM0400
illustrates