Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 276
25.8 Register description
25.8.1 MCUCR – MCU Control Register
The MCU Control Register contains control bits for general MCU functions.
Note: 1. Only available in the ATmega164PA/324PA/644PA/1284P.
• Bits 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. Note that this bit must not be altered when using the On-chip
Debug system.
25.8.2 MCUSR – MCU Status Register
The MCU Status Register provides information on which reset source caused an MCU reset.
• 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.
Bit 76 5 43210
0x35 (0x55) JTD
BODS
(1)
BODSE
(1)
PUD – – IVSEL IVCE MCUCR
Read/Write R/W R/W R/W R/W R R R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
0x34 (0x54)
– – –JTRFWDRF BORF EXTRF PORF MCUSR
Read/Write R R R R/W R/W R/W R/W R/W
Initial Value 0 0 0 See Bit Description