Run Control; Introduction To Probe Mode; Probe Mode Entry - Intel Quark SoC X1000 User Manual

Run Control

5 Run Control
5.1

Introduction to Probe Mode

Probe Mode is a debug mode of the processor in which the normal execution sequence
is interrupted. The processor enters a dormant state where architectural state can be
viewed and modified. The state extraction/modification is performed with the help of
the TAP. Special hardware/software products are developed to make use of Probe
Mode.
The processor can be made to enter Probe Mode in various ways. The PREQ (Probe
Mode Request) pin, called PREQ# is pulsed to cause Probe Mode entry. The processor
can also be configured to enter Probe Mode when certain events occur (redirecting to
Probe Mode).
Once the processor enters Probe Mode and is ready to accept commands, it pulses the
PRDY (Probe Mode Ready) pin, called PRDY#. Debug Software can then issue Probe
Mode instructions (to be described later) to access architectural state. When an
instruction is submitted while the processor is in Probe Mode, PRDY# is pulsed upon
completion of the instruction.
While in Probe Mode, all the communication between the Debug Software and the
processor is done through the TAP. The Probe Mode instructions are serially sent via
the WRSUBPIR instruction into the TAP that then transfers the instruction bytes to the
fetch unit.
Probe Mode Entry on Intel processors is an interrupt/exception style event and is
prioritized with other events. The priority is very low.
5.2

Probe Mode Entry

Probe Mode may be entered asynchronously (from the Core's perspective) by the
request of debug software using two mechanisms: the PREQ# pin and the TAP. Both
the CLTAPC and the Core TAP in the Intel
requesting entry into Probe Mode.
Some systems using the Intel
PRDY# pins to the Debug Tool's connector on the board. In these cases, the Debug
Software must rely only on the TAP for all debug activities.
The Core will pulse PRDY# for two bus clock cycles and this pulse is latched by the
CLTAPC_CPU_TAPSTATUS TDR.
The Core may be configured to enter Probe Mode when a code or data breakpoint
match occurs. These appear to be asynchronous entries in to Probe Mode from the
perspective of the Debug Software since it cannot predict when or if the breakpoint
match will occur. Any standard Debug Exception (#DB) from the core may be
Order Number: 329866-002US
®
Quark SoC X1000 have TAP instructions for
®
Quark SoC X1000 may not route the PREQ# and
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