ATmega16A datasheet(249/352 Pages) ATMEL

249 / 352 page

249

8154B–AVR–07/09

ATmega16A

Notes:

1. PRIVATE_SIGNAL1 should always be scanned in as zero.

2. PRIVATE:SIGNAL2 should always be scanned in as zero.

24.7

Boundary-scan Description Language Files

Boundary-scan Description Language (BSDL) files describe Boundary-scan capable devices in

a standard format used by automated test-generation software. The order and function of bits in

the Boundary-scan Data Register are included in this description. A BSDL file for ATmega16A is

available.

24.8

24.8.1

MCUCSR – MCU Control and Status Register

The MCU Control and Status Register contains control bits for general MCU functions, and pro-

vides information on which reset source caused an MCU Reset.

• Bit 7 – JTD: JTAG Interface Disable

When this bit is zero, the JTAG interface is enabled if the JTAGEN Fuse is programmed. If this

bit is one, the JTAG interface is disabled. In order to avoid unintentional disabling or enabling of

the JTAG interface, a timed sequence must be followed when changing this bit: The application

software must write this bit to the desired value twice within four cycles to change its value.

If the JTAG interface is left unconnected to other JTAG circuitry, the JTD bit should be set to

one. The reason for this is to avoid static current at the TDO pin in the JTAG interface.

• Bit 4 – JTRF: JTAG Reset Flag

This bit is set if a reset is being caused by a logic one in the JTAG Reset Register selected by

the JTAG instruction AVR_RESET. This bit is reset by a Power-on Reset, or by writing a logic

zero to the flag.

PA1.Control

PA1.Pullup_Enable

2PA0.Data

PA0.Control

PA0.Pullup_Enable

Table 24-8.

ATmega16A Boundary-scan Order (Continued)

Bit Number

Signal Name

Module

Bit

7654

321

JTD

ISC2

–JTRF

WDRF

BORF

EXTRF

PORF

MCUCSR

Read/Write

R/W

Initial Value

See Bit Description

ATmega16A Datasheet(PDF) 249 Page - ATMEL Corporation

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