ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 242

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

25.4.3
25.4.4
25.4.5
25.5
25.5.1
8285D–AVR–06/11
Boundary-scan Chain
SAMPLE_PRELOAD; 0x2
AVR_RESET; 0xC
BYPASS; 0xF
Scanning the Digital Port Pins
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
The active states are:
• Capture-DR: Data in the IDCODE Register is sampled into the Boundary-scan Chain.
• Shift-DR: The IDCODE scan chain is shifted by the TCK input.
Mandatory JTAG instruction for pre-loading the output latches and taking a snap-shot of the
input/output pins without affecting the system operation. However, the output latches are not
connected to the pins. The Boundary-scan Chain is selected as Data Register.
The active states are:
• Capture-DR: Data on the external pins are sampled into the Boundary-scan Chain.
• Shift-DR: The Boundary-scan Chain is shifted by the TCK input.
• Update-DR: Data from the Boundary-scan chain is applied to the output latches. However, the
The AVR specific public JTAG instruction for forcing the AVR device into the Reset mode or
releasing the JTAG reset source. The TAP controller is not reset by this instruction. The one bit
Reset Register is selected as Data Register. Note that the reset will be active as long as there is
a logic “one” in the Reset Chain. The output from this chain is not latched.
The active states are:
• Shift-DR: The Reset Register is shifted by the TCK input.
Mandatory JTAG instruction selecting the Bypass Register for Data Register.
The active states are:
• Capture-DR: Loads a logic “0” into the Bypass Register.
• Shift-DR: The Bypass Register cell between TDI and TDO is shifted.
The Boundary-scan chain has the capability of driving and observing the logic levels on the digi-
tal I/O pins, as well as the boundary between digital and analog logic for analog circuitry having
off-chip connection.
Figure 25-3 on page 243
function. The cell consists of a standard Boundary-scan cell for the Pull-up Enable – PUExn –
function, and a bi-directional pin cell that combines the three signals Output Control – OCxn,
Output Data – ODxn, and Input Data – IDxn, into only a two-stage Shift Register. The port and
pin indexes are not used in the following description
The Boundary-scan logic is not included in the figures in the datasheet.
shows a simple digital port pin as described in the section
ary-scan details from
244.
output latches are not connected to the pins.
Figure 25-3 on page 243
shows the Boundary-scan Cell for a bi-directional port pin with pull-up
replaces the dashed box in
”I/O-Ports” on page
Figure 25-4 on page 244
Figure 25-4 on page
68. The Bound-
242