Hi-Z (B[3:0] = 0100); Enable_Once(B[3:0] = 0110); Debug_Request(B[3:0] = 0111) - Motorola DSP56305 User Manual

Register, the required guarding signals would be loaded as part of the complete serial
data stream shifted in, both at the start of the test and each time a new test pattern is
entered. Since the CLAMP instruction allows guarding values to be applied using the
Boundary Scan Register of the appropriate ICs while selecting their Bypass registers, it
allows much faster testing than does the EXTEST instruction. Data in the boundary scan
cell remains unchanged until a new instruction is shifted in or the JTAG state machine is
set to its reset state. The CLAMP instruction also asserts internal reset for the DSP56300
core system logic to force a predictable internal state while performing external
boundary scan operations.
11.3.2.5

HI-Z (B[3:0] = 0100)

The HI-Z instruction is not included in the IEEE 1149.1 standard. It is provided as a
manufacturer's optional public instruction to prevent having to backdrive the output
signals during circuit-board testing. When HI-Z is invoked, all output drivers, including
the two-state drivers, are turned off (i.e., high impedance). The instruction selects the
Bypass register. The HI-Z instruction also asserts internal reset for the DSP56300 core
system logic to force a predictable internal state while performing external boundary
scan operations
11.3.2.6

ENABLE_ONCE(B[3:0] = 0110)

The ENABLE_ONCE instruction is not included in the IEEE 1149.1 standard. It is
provided as a public instruction to allow the user to perform system debug functions.
When the ENABLE_ONCE instruction is decoded the TDI and TDO signals are
connected directly to the OnCE registers. The particular OnCE register connected
between TDI and TDO at a given time is selected by the OnCE controller depending on
the OnCE instruction currently being executed. All communication with the OnCE
controller is done through the Select-DR-Scan path of the JTAG TAP Controller.
Section 10, On-Chip Emulation (OnCE)
11.3.2.7

DEBUG_REQUEST(B[3:0] = 0111)

The DEBUG_REQUEST instruction is not included in the IEEE 1149.1 standard. It is
provided as a public instruction to allow the user to generate a debug request signal to
the DSP56300 core. When the DEBUG_REQUEST instruction is decoded, the TDI and
TDO signals are connected to the Instruction Registers. Due to the fact that in the
Capture-IR state of the TAP the OnCE status bits are captured in the Instruction shift
register, the external JTAG controller must continue to shift-in the DEBUG_REQUEST
instruction while polling the status bits that are shifted-out until the Debug mode of
operation is entered (acknowledged by the combination 11 on OS1–OS0). After
acknowledgment of the Debug mode is received, the external JTAG controller must issue
the ENABLE_ONCE instruction to allow the user to perform system debug functions.
MOTOROLA
, for more information.
DSP56305 User's Manual
JTAG Port
TAP Controller
See
11-11