atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 218

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Figure 24-1. Block Diagram
218
TDI
TDO
TCK
TMS
ATmega325/3250/645/6450
CONTROLLER
M
U
X
TAP
DEVICE BOUNDARY
INSTRUCTION
BREAKPOINT
SCAN CHAIN
REGISTER
REGISTER
REGISTER
BYPASS
ID
•
The IEEE std. 1149.1 also specifies an optional TAP signal; TRST – Test ReSeT – which is not
provided.
When the JTAGEN fuse is unprogrammed, these four TAP pins are normal port pins and the
TAP controller is in reset. When programmed and the JTD bit in MCUCSR is cleared, the TAP
pins are internally pulled high and the JTAG is enabled for Boundary-scan and programming.
The device is shipped with this fuse programmed.
For the On-chip Debug system, in addition to the JTAG interface pins, the RESET pin is moni-
tored by the debugger to be able to detect external reset sources. The debugger can also pull
the RESET pin low to reset the whole system, assuming only open collectors on the reset line
are used in the application.
DECODER
ADDRESS
TDO: Test Data Out. Serial output data from Instruction Register or Data Register.
JTAG PROGRAMMING
MEMORY
FLASH
AND CONTROL
BREAKPOINT
OCD STATUS
INTERFACE
UNIT
Address
Data
I/O PORT 0
I/O PORT n
INTERNAL
FLOW CONTROL
CHAIN
SCAN
UNIT
BOUNDARY SCAN CHAIN
PC
Instruction
COMMUNICATION
JTAG / AVR CORE
PERIPHERAL
INTERFACE
AVR CPU
DIGITAL
UNITS
PERIPHERIAL
ANALOG
UNITS
2570L–AVR–08/07
Analog inputs
Control & Clock lines