The AT90USB64/128 provides the following features: 64/128K bytes of In-System Programma-
ble Flash with Read-While-Write capabilities, 2K/4K bytes EEPROM, 4K/8K bytes SRAM, 48
general purpose I/O lines, 32 general purpose working registers, Real Time Counter (RTC), four
flexible Timer/Counters with compare modes and PWM, one USART, a byte oriented 2-wire
Serial Interface, a 8-channels, 10-bit ADC with optional differential input stage with programma-
ble gain, programmable Watchdog Timer with Internal Oscillator, an SPI serial port, IEEE std.
1149.1 compliant JTAG test interface, also used for accessing the On-chip Debug system and
programming and six software selectable power saving modes. The Idle mode stops the CPU
while allowing the SRAM, Timer/Counters, SPI port, and interrupt system to continue function-
ing. The Power-down mode saves the register contents but freezes the Oscillator, disabling all
other chip functions until the next interrupt or Hardware Reset. In Power-save mode, the asyn-
chronous timer continues to run, allowing the user to maintain a timer base while the rest of the
device is sleeping. The ADC Noise Reduction mode stops the CPU and all I/O modules except
Asynchronous Timer and ADC, to minimize switching noise during ADC conversions. In Standby
mode, the Crystal/Resonator Oscillator is running while the rest of the device is sleeping. This
allows very fast start-up combined with low power consumption. In Extended Standby mode,
both the main Oscillator and the Asynchronous Timer continue to run.
The device is manufactured using Atmel’s high-density nonvolatile memory technology. The On-
chip ISP Flash allows the program memory to be reprogrammed in-system through an SPI serial
interface, by a conventional nonvolatile memory programmer, or by an On-chip Boot program
running on the AVR core. The boot program can use any interface to download the application
program in the application Flash memory. Software in the Boot Flash section will continue to run
while the Application Flash section is updated, providing true Read-While-Write operation. By
combining an 8-bit RISC CPU with In-System Self-Programmable Flash on a monolithic chip,
the Atmel AT90USB64/128 is a powerful microcontroller that provides a highly flexible and cost
effective solution to many embedded control applications.
The AT90USB64/128 AVR is supported with a full suite of program and system development
tools including: C compilers, macro assemblers, program debugger/simulators, in-circuit emula-
tors, and evaluation kits.
2.2
Pin Descriptions
2.2.1
VCC
Digital supply voltage.
2.2.2
2.2.3
GND
Ground.
Port A (PA7..PA0)
Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port A output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port A pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port A pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port A also serves the functions of various special features of the AT90USB64/128 as listed on
page 80.
6
AT90USB64/128
7593A–AVR–02/06
ATMEL [ ATMEL ]
