73
AT94KAL Series FPSLIC
Rev. 1138G–FPSLI–11/03
On-chip Debug
Specific JTAG
Instructions
The On-Chip debug support is considered being private JTAG instructions, and distributed
within ATMEL and to selected third-party vendors only. Table 17 lists the instruction opcode.
IEEE 1149.1
(JTAG)
Boundary-scan
Features
•
JTAG (IEEE std. 1149.1 compliant) Interface
•
Boundary-scan Capabilities According to the JTAG Standard
•
Full Scan of All Port Functions
•
Supports the Optional IDCODE Instruction
•
Additional Public AVR_RESET Instruction to Reset the AVR
System Overview
The Boundary-Scan chain has the capability of driving and observing the logic levels on the
AVR’s digital I/O pins. At system level, all ICs having JTAG capabilities are connected serially
by the TDI/TDO signals to form a long shift register. An external controller sets up the devices
to drive values at their output pins, and observe the input values received from other devices.
The controller compares the received data with the expected result. In this way, Boundary-
Scan provides a mechanism for testing interconnections and integrity of components on
Printed Circuits Boards by using the 4 TAP signals only.
The four IEEE 1149.1 defined mandatory JTAG instructions IDCODE, BYPASS, SAM-
PLE/PRELOAD, and EXTEST, as well as the AVR specific public JTAG instruction
AVR_RESET can be used for testing the Printed Circuit Board. Initial scanning of the data reg-
ister path will show the ID-code of the device, since IDCODE is the default JTAG instruction. It
may be desirable to have the AVR device in reset during test mode. If not reset, inputs to the
device may be determined by the scan operations, and the internal software may be in an
Table 17.
JTAG Instruction and Code
JTAG Instruction
4-bit Code
Selected Scan Chain
# Bits
EXTEST
$0 (0000)
AVR I/O Boundary
69
IDCODE
$1 (0001)
Device ID
32
SAMPLE_PRELOAD
$2 (0010)
AVR I/O Boundary
69
RESERVED
$3 (0011)
N/A
–
PRIVATE
$4 (0100)
FPSLIC On-chip Debug System
–
PRIVATE
$5 (0101)
FPSLIC On-chip Debug System
–
PRIVATE
$6 (0110)
FPSLIC On-chip Debug System
–
RESERVED
$7 (0111)
N/A
–
PRIVATE
$8 (1000)
FPSLIC On-chip Debug System
–
PRIVATE
$9 (1001)
FPSLIC On-chip Debug System
–
PRIVATE
$A (1010)
FPSLIC On-chip Debug System
–
PRIVATE
$B (1011)
FPSLIC On-chip Debug System
–
AVR_RESET
$C (1100)
AVR Reset
1
RESERVED
$D (1101)
N/A
–
RESERVED
$E (1110)
N/A
–
BYPASS
$F (1111)
Bypass
1