4
AT90S8515
0841GS–09/01
one clock cycle. The resulting architecture is more code efficient while achieving
throughputs up to ten times faster than conventional CISC microcontrollers.
The AT90S8515 provides the following features: 8K bytes of In-System Programmable
Flash, 512 bytes EEPROM, 512 bytes SRAM, 32 general-purpose I/O lines, 32 general-
purpose working registers, flexible timer/counters with compare modes, internal and
external interrupts, a programmable serial UART, programmable Watchdog Timer with
internal oscillator, an SPI serial port and two software-selectable power-saving modes.
The Idle Mode stops the CPU while allowing the SRAM, timer/counters, SPI port and
interrupt system to continue functioning. The Power-down mode saves the register con-
tents but freezes the oscillator, disabling all other chip functions until the next external
interrupt or hardware reset.
The device is manufactured using Atmel’s high-density nonvolatile memory technology.
The On-chip In-System Programmable Flash allows the program memory to be repro-
grammed In-System through an SPI serial interface or by a conventional nonvolatile
memory programmer. By combining an enhanced RISC 8-bit CPU with In-System Pro-
grammable Flash on a monolithic chip, the Atmel AT90S8515 is a powerful
microcontroller that provides a highly flexible and cost-effective solution to many embed-
ded control applications.
The AT90S8515 AVR is supported with a full suite of program and system development
tools including: C compilers, macro assemblers, program debugger/simulators, in-circuit
emulators and evaluation kits.
Pin Descriptions
VCC
Supply voltage.
GND
Ground.
Port A (PA7..PA0)
Port A is an 8-bit bi-directional I/O port. Port pins can provide internal pull-up resistors
(selected for each bit). The Port A output buffers can sink 20 mA and can drive LED dis-
plays directly. When pins PA0 to PA7 are used as inputs and are externally pulled low,
they will source current if the internal pull-up resistors are activated. The Port A pins are
tri-stated when a reset condition becomes active, even if the clock is not active.
Port A serves as multiplexed address/data input/output when using external SRAM.
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors. The Port B output
buffers can sink 20 mA. As inputs, Port B pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset
condition becomes active, even if the clock is not active.
Port B also serves the functions of various special features of the AT90S8515 as listed
on page 66.
Port C (PC7..PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors. The Port C output
buffers can sink 20 mA. As inputs, Port C pins that are externally pulled low will source
current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset
condition becomes active, even if the clock is not active.
Port C also serves as address output when using external SRAM.
Port D (PD7..PD0)
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors. The Port D output
buffers can sink 20 mA. As inputs, Port D pins that are externally pulled low will source
