413
8331B–AVR–03/12
Atmel AVR XMEGA AU
31.5.2
Scanning the PDI Pins
Two observe-only cells are inserted to make the combined RESET and PDI_CLK pin and the
PDI_DATA pin observable. Even though the PDI_DATA pin is bidirectional, it is only made
observable in order to avoid any extra logic on the PDI_DATA output path.
Figure 31-3.
An observe-only input cell.
31.6
Data Registers
The supported data registers that can be connected between TDI and TDO are:
• Bypass register (Ref: register A in
• Device identification register (Ref: register C in
).
• Boundary scan chain (Ref: register D in
• PDICOM data register (Ref: register B in
Figure 31-4.
JTAG data register overview.
D Q
From last
cell
Clock DR
To next cell
To system
logic
From system
pin
Sh
ift DR
1
0
D
D
TDI
A
B
B
B
C
C
C
C
TDO
TMS
D
D
D
D
D
D
D
D
D
I/O PORTS
PDI
JTAG
TCK
to all TCK
registers
Internal registers
JT
AG
Bou
nda
ry-
s
ca
n c
h
ai
n
TAP
CTRL