Atmel AVR AT90S2323 User manual

Features

•Utilizes the AVR®RISC Architecture

•AVR – High-performance and Low-power RISC Architecture

– 118 Powerful Instructions – Most Single Clock Cycle Execution

– 32 x 8 General-purpose Working Registers

– Up to 10 MIPS Throughput at 10 MHz

•Data and Nonvolatile Program Memory

– 2K Bytes of In-System Programmable Flash

Endurance: 1,000 Write/Erase Cycles

– 128 Bytes Internal RAM

– 128 Bytes of In-System Programmable EEPROM

Endurance: 100,000 Write/Erase Cycles

– Programming Lock for Flash Program and EEPROM Data Security

•Peripheral Features

– One 8-bit Timer/Counter with Separate Prescaler

– Programmable Watchdog Timer with On-chip Oscillator

– SPI Serial Interface for In-System Programming

•Special Microcontroller Features

– Low-power Idle and Power-down Modes

– External and Internal Interrupt Sources

– Power-on Reset Circuit

– Selectable On-chip RC Oscillator

•Specifications

– Low-power, High-speed CMOS Process Technology

– Fully Static Operation

•Power Consumption at 4 MHz, 3V, 25°C

– Active: 2.4 mA

– Idle Mode: 0.5 mA

– Power-down Mode: <1 µA

•I/O and Packages

– Three Programmable I/O Lines for AT90S/LS2323

– Five Programmable I/O Lines for AT90S/LS2343

– 8-pin PDIP and SOIC

•Operating Voltages

– 4.0 - 6.0V for AT90S2323/AT90S2343

– 2.7 - 6.0V for AT90LS2323/AT90LS2343

•Speed Grades

– 0 - 10 MHz for AT90S2323/AT90S2343-10

– 0 - 4 MHz for AT90LS2323/AT90LS2343-4

– 0 - 1 MHz for AT90LS2343-1

Pin Configuration

PDIP/SOIC

RESET

XTAL1

XTAL2

GND

VCC

PB2 (SCK/T0)

PB1 (MISO/INT0)

PB0 (MOSI)

AT90S/LS2323

RESET

(CLOCK) PB3

PB4

GND

VCC

PB2 (SCK/T0)

PB1 (MISO/INT0)

PB0 (MOSI)

AT90S/LS2343

8-bit

Microcontroller

with 2K Bytes of

In-System

Programmable

Flash

AT90S2323

AT90LS2323

AT90S2343

AT90LS2343

Rev. 1004D–09/01

2AT90S/LS2323/2343

1004D–09/01

Description The AT90S/LS2323 and AT90S/LS2343 are low-power, CMOS, 8-bit microcontrollers

based on the AVR RISC architecture. By executing powerful instructions in a single

clock cycle, the AT90S2323/2343 achieves throughputs approaching 1 MIPS per MHz

allowing the system designer to optimize power consumption versus processing speed.

The AVR core combines a rich instruction set with 32 general-purpose working regis-

ters. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU),

allowing two independent registers to be accessed in one single instruction executed in

one clock cycle. The resulting architecture is more code efficient while achieving

throughputs up to ten times faster than conventional CISC microcontrollers.

Block Diagram Figure 1. The AT90S/LS2343 Block Diagram

PROGRAM

COUNTER

INTERNAL

OSCILLATOR

WATCHDOG

TIMER

STACK

POINTER

PROGRAM

FLASH

MCU CONTROL

SRAM

GENERAL

PURPOSE

REGISTERS

INSTRUCTION

TIMER/

COUNTER

INSTRUCTION

DECODER

DATA DIR.

REG. PORTB

DATA REGISTER

PORTB

PROGRAMMING

LOGIC

TIMING AND

CONTROL

INTERRUPT

UNIT

EEPROM

SPI

STATUS

ALU

PORTB DRIVERS

PB0 - PB4

RESET

VCC

GND

CONTROL

LINES

8-BIT DATA BUS

AT90S/LS2323/2343

1004D–09/01

Figure 2. The AT90S/LS2323 Block Diagram

The AT90S2323/2343 provides the following features: 2K bytes of In-System Program-

mable Flash, 128 bytes EEPROM, 128 bytes SRAM, 3 (AT90S/LS2323)/5

(AT90S/LS2343) general-purpose I/O lines, 32 general-purpose working registers, an 8-

bit timer/counter, internal and external interrupts, programmable Watchdog Timer with

internal oscillator, an SPI serial port for Flash Memory downloading 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 contents but freezes the oscillator, disabling all

other chip functions until the next interrupt or hardware reset.

The device is manufactured using Atmel’s high-density nonvolatile memory technology.

The On-chip Flash allows the program memory to be reprogrammed in-system through

an SPI serial interface. By combining an 8-bit RISC CPU with ISP Flash on a monolithic

PROGRAM

COUNTER

INTERNAL

OSCILLATOR

WATCHDOG

TIMER

STACK

POINTER

PROGRAM

FLASH

MCU CONTROL

SRAM

GENERAL

PURPOSE

REGISTERS

INSTRUCTION

TIMER/

COUNTER

INSTRUCTION

DECODER

DATA DIR.

REG. PORTB

DATA REGISTER

PORTB

PROGRAMMING

LOGIC

TIMING AND

CONTROL

OSCILLATOR

INTERRUPT

UNIT

EEPROM

SPI

STATUS

ALU

PORTB DRIVERS

PB0 - PB2

RESET

VCC

GND

CONTROL

LINES

8-BIT DATA BUS

4AT90S/LS2323/2343

1004D–09/01

chip, the Atmel AT90S2323/2343 is a powerful microcontroller that provides a highly

flexible and cost-effective solution to many embedded control applications.

The AT90S2323/2343 AVR is supported with a full suite of program and system devel-

opment tools including: C compilers, macro assemblers, program debugger/simulators,

in-circuit emulators and evaluation kits.

Comparison between

AT90S/LS2323 and

AT90S/LS2343

The AT90S/LS2323 is intended for use with external quartz crystal or ceramic resonator

as the clock source. The start-up time is fuse-selectable as either 1 ms (suitable for

ceramic resonator) or 16 ms (suitable for crystal). The device has three I/O pins.

The AT90S/LS2343 is intended for use with either an external clock source or the inter-

nal RC oscillator as clock source. The device has five I/O pins.

Table 1 summarizes the differences in features of the two devices.

Pin Descriptions

AT90S/LS2323

VCC Supply voltage pin.

GND Ground pin.

Port B (PB2..PB0) Port B is a 3-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.

Port B also serves the functions of various special features.

Port pins can provide internal pull-up resistors (selected for each bit). The Port B pins

are tri-stated when a reset condition becomes active.

RESET Reset input. An external reset is generated by a low level on the RESET pin. Reset

pulses longer than 50 ns will generate a reset, even if the clock is not running. Shorter

pulses are not guaranteed to generate a reset.

XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit.

XTAL2 Output from the inverting oscillator amplifier.

Table 1. Feature Difference Summary

Part AT90S/LS2323 AT90S/LS2343

On-chip Oscillator Amplifier yes no

Internal RC Clock no yes

PB3 available as I/O pin never internal clock mode

PB4 available as I/O pin never always

Start-up time 1 ms/16 ms 16 µs fixed

AT90S/LS2323/2343

1004D–09/01

Pin Descriptions

AT90S/LS2343

VCC Supply voltage pin.

GND Ground pin.

Port B (PB4..PB0) Port B is a 5-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.

Port B also serves the functions of various special features.

Port pins can provide internal pull-up resistors (selected for each bit). The Port B pins

are tri-stated when a reset condition becomes active.

RESET Reset input. An external reset is generated by a low level on the RESET pin. Reset

pulses longer than 50 ns will generate a reset, even if the clock is not running. Shorter

pulses are not guaranteed to generate a reset.

CLOCK Clock signal input in external clock mode.

Clock Options

Crystal Oscillator The AT90S/LS2323 contains an inverting amplifier that can be configured for use as an

On-chip oscillator, as shown in Figure 3. XTAL1 and XTAL2 are input and output

respectively. Either a quartz crystal or a ceramic resonator may be used. It is recom-

mended that the AT90S/LS2343 be used if an external clock source is used, since this

gives an extra I/O pin.

Figure 3. Oscillator Connection

External Clock The AT90S/LS2343 can be clocked by an external clock signal, as shown in Figure 4, or

by the On-chip RC oscillator. This RC oscillator runs at a nominal frequency of 1 MHz

(VCC = 5V). A fuse bit (RCEN) in the Flash memory selects the On-chip RC oscillator as

the clock source when programmed (“0”). The AT90S/LS2343 is shipped with this bit

programmed. The AT90S/LS2343 is recommended if an external clock source is used,

because this gives an extra I/O pin.

The AT90S/LS2323 can be clocked by an external clock as well, as shown in Figure 4.

No fuse bit selects the clock source for AT90S/LS2323.

6AT90S/LS2323/2343

1004D–09/01

Figure 4. External Clock Drive Configuration

GND

EXTERNAL

OSCILATOR

SIGNAL

EXTERNAL

OSCILATOR

SIGNAL

NC XTAL2

XTAL1

PB3

AT90S/LS2323AT90S/LS2343

AT90S/LS2323/2343

1004D–09/01

Architectural

Overview

The fast-access register file concept contains 32 x 8-bit general-purpose working regis-

ters with a single clock cycle access time. This means that during one single clock cycle,

one ALU (Arithmetic Logic Unit) operation is executed. Two operands are output from

the register file, the operation is executed and the result is stored back in the register file

–in one clock cycle.

Six of the 32 registers can be used as three 16-bit indirect address register pointers for

Data Space addressing, enabling efficient address calculations. One of the three

address pointers is also used as the address pointer for the constant table look-up func-

tion. These added function registers are the 16-bit X-, Y-, and Z-register.

Figure 5. The AT90S2323/2343 AVR RISC Architecture

The ALU supports arithmetic and logic functions between registers or between a con-

stant and a register. Single register operations are also executed in the ALU. Figure 5

shows the AT90S2323/2343 AVR RISC microcontroller architecture.

In addition to the register operation, the conventional memory addressing modes can be

used on the register file as well. This is enabled by the fact that the register file is

assigned the 32 lowermost Data Space addresses ($00 - $1F), allowing them to be

accessed as though they were ordinary memory locations.

The I/O memory space contains 64 addresses for CPU peripheral functions such as

Control Registers, Timer/Counters, A/D converters and other I/O functions. The I/O

memory can be accessed directly or as the Data Space locations following those of the

1K x 16

Program

Flash

Instruction

Decoder

Program

Counter

Control Lines

32 x 8

General

Purpose

Registers

ALU

Status

and Test

Control

Registers

Interrupt

Unit

SPI

Unit

8-bit

Timer/Counter

Watchdog

Timer

I/O Lines

128 x 8

EEPROM

Data Bus 8-bit

128 x 8

Data

SRAM

Direct Addressing

Indirect Addressing

8AT90S/LS2323/2343

1004D–09/01

The AVR has Harvard architecture –with separate memories and buses for program

and data. The program memory is accessed with a two-stage pipeline. While one

instruction is being executed, the next instruction is pre-fetched from the program mem-

ory. This concept enables instructions to be executed in every clock cycle. The program

memory is in-system downloadable Flash memory.

With the relative jump and call instructions, the whole 1K address space is directly

accessed. Most AVR instructions have a single 16-bit word format. Every program

memory address contains a 16- or 32-bit instruction.

During interrupts and subroutine calls, the return address Program Counter (PC) is

stored on the stack. The stack is effectively allocated in the general data SRAM and

consequently, the stack size is only limited by the total SRAM size and the usage of the

SRAM. All user programs must initialize the SP in the reset routine (before subroutines

or interrupts are executed). The 8-bit stack pointer (SP) is read/write-accessible in the

I/O space.

The 128 bytes data SRAM + register file and I/O registers can be easily accessed

through the five different addressing modes supported in the AVR architecture.

The memory spaces in the AVR architecture are all linear and regular memory maps.

Figure 6. Memory Maps

A flexible interrupt module has its control registers in the I/O space with an additional

global interrupt enable bit in the status register. All the different interrupts have a sepa-

rate interrupt vector in the interrupt vector table at the beginning of the program

memory. The different interrupts have priority in accordance with their interrupt vector

position. The lower the interrupt vector address, the higher the priority.

EEPROM

(128 x 8)

$000

$07F

EEPROM Data Memory

AT90S/LS2323/2343

1004D–09/01

General-purpose

Figure 7 shows the structure of the 32 general-purpose registers in the CPU.

Figure 7. AVR CPU General-purpose Working Registers

All the register operating instructions in the instruction set have direct and single-cycle

access to all registers. The only exception is the five constant arithmetic and logic

instructions SBCI, SUBI, CPI, ANDI and ORI between a constant and a register and the

LDI instruction for load immediate constant data. These instructions apply to the second

half of the registers in the register file (R16..R31). The general SBC, SUB, CP, AND and

OR and all other operations between two registers or on a single register apply to the

entire register file.

As shown in Figure 7, each register is also assigned a data memory address, mapping

them directly into the first 32 locations of the user Data Space. Although the register file

is not physically implemented as SRAM locations, this memory organization provides

great flexibility in access of the registers, as the X-, Y-, and Z-registers can be set to

index any register in the file.

70Addr.

R0 $00

R1 $01

R2 $02

…

R13 $0D

General R14 $0E

Purpose R15 $0F

Working R16 $10

Registers R17 $11

…

R26 $1A X-register low byte

R27 $1B X-register high byte

R28 $1C Y-register low byte

R29 $1D Y-register high byte

R30 $1E Z-register low byte

R31 $1F Z-register high byte

10 AT90S/LS2323/2343

1004D–09/01

X-register, Y-register and Z-

The registers R26..R31 have some added functions to their general-purpose usage.

These registers are the address pointers for indirect addressing of the Data Space. The

three indirect address registers X, Y, and Z, are defined in Figure 8.

Figure 8. The X-, Y-, and Z-registers

In the different addressing modes, these address registers have functions as fixed dis-

placement, automatic increment and decrement (see the descriptions for the different

instructions).

ALU –Arithmetic Logic

Unit

The high-performance AVR ALU operates in direct connection with all the 32 general-

purpose working registers. Within a single clock cycle, ALU operations between regis-

ters in the register file are executed. The ALU operations are divided into three main

categories: arithmetic, logic and bit functions.

In-System

Programmable Flash

Program Memory

The AT90S2323/2343 contains 2K bytes On-chip, In-System Programmable Flash

memory for program storage. Since all instructions are 16- or 32-bit words, the Flash is

organized as 1K x 16. The Flash memory has an endurance of at least 1000 write/erase

cycles.

The AT90S2323/2343 Program Counter (PC) is 10 bits wide, hence addressing the

1024 program memory addresses. See page 42 for a detailed description on Flash data

programming.

Constant tables must be allocated within the address 0 - 2K (see the LPM –Load Pro-

gram Memory instruction description on page 60).

See page 12 for the different addressing modes.

EEPROM Data Memory The AT90S2323/2343 contains 128 bytes of EEPROM data memory. It is organized as

a separate data space, in which single bytes can be read and written. The EEPROM has

an endurance of at least 100,000 write/erase cycles. The access between the EEPROM

and the CPU is described on page 32, specifying the EEPROM address register, the

EEPROM data register and the EEPROM control register.

For the SPI data downloading, see page 42 for a detailed description.

15 0

X-register 7 0 7 0

R27 ($1B) R26 ($1A)

15 0

Y-register 7 0 7 0

R29 ($1D) R28 ($1C)

15 0

Z-register 7 0 7 0

R31 ($1F) R30 ($1E)

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