ATmega1284 / ATmega1284P / ATmega644 / ATmega32 connection guide
ATmega1284 / ATmega1284P / ATmega644 / ATmega32 QFN-44 wiring guide with power, signal assignments, and bench checks.
32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
Power and reset
RequiredUse a current-limited supply at a voltage permitted by the order code and system clock. Tie the listed supply pins to that rail. Fit one 100 nF ceramic capacitor close to each supply-and-ground pair. Use a 10 kΩ reset pull-up for this bench circuit.
- Target rail
- Ground
- Reset
Bench checks
- With power off, check for a short across the supply. Power on and measure voltage at every supply pin and at reset.
- Check the clock source configured by CKSEL. If a used part expects an external clock, provide it before attempting serial programming.
AN2519 §§2–3 and 2503Q · Pin descriptions and clock source
Connection scenarios
Program and read the signature over ISP
Start from the power and reset circuit. Attach a voltage-compatible AVR in-system programmer and use the target voltage as its reference. Connect reset, serial data in/out, and SCK as shown.
- Target voltage sense
- Common ground
- Reset assertion
- Programmer RESET
- RESET (4)
- Serial data into target
- Programmer MOSI
- PB5 (1)
- Serial data out of target
- Programmer MISO
- PB6 (2)
- Programming clock
- Programmer SCK
- PB7 (3)
Bench checks
- Read the device signature before writing flash or fuses. If it fails, verify target power, the clock source, programmer direction, and the selected device.
- If the programmer offers an adjustable SCK, start below one quarter of the target clock and check the data sheet’s SCK high and low timing. Disconnect or isolate other peripherals that drive the programming lines.
- Disable power output on the programmer if the target has its own bench supply. Confirm the programmer’s VTG behavior in its manual.
AN2519 §4.1 and 2503Q · Serial Programming Pin Mapping
QFN-44 wiring map
EP is the exposed center pad on the underside.
1 · PB5
General-purpose digital I/O. Alternate assignments: MOSI (SPI).
After reset · GPIO driver is high impedance during reset. Clock, debug, and alternate-function use depend on fuse and peripheral configuration.
Models and documents
Each package lists the documented order codes and variants covered by this map. Select the marked model to see its peripheral assignments and memory. Check the exact order code and datasheet revision before laying out a PCB.
- ATmega1284
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
- ATmega1284-MU
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
- ATmega1284-MUR
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
- ATmega1284P
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
- ATmega1284P-MU
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
- ATmega1284P-MUR
- 128 KiB flash · 16 KiB SRAM · 4 KiB EEPROM · 1.8–5.5 V · 20 MHz maximum · -40 to +85 °C
- ATmega644
- 64 KiB flash · 4 KiB SRAM · 2 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
- ATmega644V-10MU
- 64 KiB flash · 4 KiB SRAM · 2 KiB EEPROM · 1.8–5.5 V · 10 MHz maximum · -40 to +85 °C
- ATmega644-20MU
- 64 KiB flash · 4 KiB SRAM · 2 KiB EEPROM · 2.7–5.5 V · 20 MHz maximum · -40 to +85 °C
- ATmega32
- 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM. Choose the marked order code for voltage, clock, and temperature.
- ATmega32L-8MU
- 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +85 °C
- ATmega32L-8MUR
- 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 2.7–5.5 V · 8 MHz maximum · -40 to +85 °C
- ATmega32-16MU
- 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +85 °C
- ATmega32-16MUR
- 32 KiB flash · 2 KiB SRAM · 1 KiB EEPROM · 4.5–5.5 V · 16 MHz maximum · -40 to +85 °C
- ATmega1284/ATmega1284P data sheet· DS40002070B · Pin configuration, electrical characteristics, ordering table and serial programming.
- ATmega644 data sheet· 2593O · Pin configuration, electrical characteristics, ordering table and serial programming.
- ATmega32 data sheet· 2503Q · Pin configuration, electrical characteristics, ordering table and serial programming.
- ATmega_DFP Device Family Pack· Machine-readable device definition: package contacts, peripheral routes, and memory sizes.
- AVR Microcontroller Hardware Design Considerations· Power supply, reset network, and programmer connection guidance.
- ATmega1284 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
- ATmega1284P documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
- ATmega644 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
- ATmega32 documentation and errata· Check current manufacturer documentation, ordering status and silicon revision applicability.
- AVR source register· Source identifiers, applicability, retrieval dates, and SHA-256 digests.