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Debugging and monitoring, 1 testability (jtag), 1 mandatory instruction support – AMD Geode SC3200 User Manual

Page 349: 2 optional instruction support, 3 jtag chain, Testability (jtag), Table 8-1, Jtag mode instruction support, 0 debugging and monitoring

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AMD Geode™ SC3200 Processor Data Book

349

8

Debugging and Monitoring

32581C

8.0

Debugging and Monitoring

8.1

Testability (JTAG)

The Test Access Port (TAP) allows board level interconnec-
tion verification and chip production tests. An IEEE-
1149.1a compliant test interface, TAP supports all IEEE
mandatory instructions as well as several optional instruc-
tions for added functionality. See Table 8-1 • for a summary
of all instructions support. For further information on JTAG,
refer to IEEE Standard 1149.1a-1993 Test Access Port and
Boundary-Scan Architecture.

8.1.1

Mandatory Instruction Support

The TAP supports all IEEE mandatory instructions, includ-
ing:

BYPASS.

Presents the shortest path through a given chip (a 1-bit
shift register).

EXTEST

Drives data loaded into the JTAG path (possibly with a
SAMPLE/PRELOAD instruction) to output pins.

SAMPLE/PRELOAD

Captures chip inputs and outputs.

8.1.2

Optional Instruction Support

The TAP supports the following IEEE optional instructions:

IDCODE

Presents the contents of the Device Identification
register in serial format.

CLAMP

Ensures that the Bypass register is connected between
TDI and TDO, and then drives data that was loaded into
the Boundary Scan register (e.g., via SAMPLE-
PRELOAD instruction) to output signals. These signals
do not change while the CLAMP instruction is selected.

HiZ

Puts all chip outputs in inactive (floating) state
(including all pins that do not require a TRI-STATE
output for normal functionality). Note that not all pull-up
resistors are disabled in this state.

8.1.3

JTAG Chain

Balls that are not part of the JTAG chain:

USB I/Os

Table 8-1. JTAG Mode Instruction Support

Code

Instruction

Activity

000

EXTEST

Drives shifted data to output pins.

001

SAMPLE/PRELOAD

Captures inputs and system outputs.

010

IDCODE

Scans out device identifier.

011

HIZ

Puts all output and bidirectional pins in TRI-STATE.

100

CLAMP

Drives fixed data from Boundary Scan register.

101

Reserved

110

Reserved

111

BYPASS

Presents shortest external path through device.