Atmel AT90S2313 User manual

1
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 of SRAM
– 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
– One 16-bit Timer/Counter with Separate Prescaler,
Compare, Capture Modes and 8-, 9- or 10-bit PWM
– On-chip Analog Comparator
– Programmable Watchdog Timer with On-chip Oscillator
– SPI Serial Interface for In-System Programming
– Full Duplex UART
•• Special Microcontroller Features
– Low-power Idle and Power-down Modes
– External and Internal Interrupt Sources
•• Specifications
– Low-power, High-speed CMOS Process Technology
– Fully Static Operation
•Power Consumption at 4 MHz, 3V, 25°C
– Active: 2.8 mA
– Idle Mode: 0.8 mA
– Power-down Mode: <1 µA
•I/O and Packages
– 15 Programmable I/O Lines
– 20-pin PDIP and SOIC
•Operating Voltages
– 2.7 - 6.0V (AT90S2313-4)
– 4.0 - 6.0V (AT90S2313-10)
•Speed Grades
– 0 - 4 MHz (AT90S2313-4)
– 0 - 10 MHz (AT90S2313-10)
Rev. 0839G–08/01
8-bit
Microcontroller
with 2K Bytes
of In-System
Programmable
Flash
AT90S2313
Pin Configuration
PDIP/SOIC

2AT90S2313
0839G–08/01
Description The AT90S2313 is a low-power CMOS 8-bit microcontroller based on the AVR RISC
architecture. By executing powerful instructions in a single clock cycle, the AT90S2313
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.
Figure 1. The AT90S2313 Block Diagram
The AT90S2313 provides the following features: 2K bytes of In-System Programmable
Flash, 128 bytes EEPROM, 128 bytes SRAM, 15 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 for Flash memory downloading and two software

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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 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 AT90S2313 is a powerful
microcontroller that provides a highly flexible and cost-effective solution to many embed-
ded control applications.
The AT90S2313 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 pin.
GND Ground pin.
Port B (PB7..PB0) Port B is an 8-bit bi-directional I/O port. Port pins can provide internal pull-up resistors
(selected for each bit). PB0 and PB1 also serve as the positive input (AIN0) and the
negative input (AIN1), respectively, of the on-chip analog comparator. The Port B output
buffers can sink 20 mA and can drive LED displays directly. When pins PB0 to PB7 are
used as inputs and are externally pulled low, they will source current if the internal 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 AT90S2313 as listed
on page 53.
Port D (PD6..PD0) Port D has seven bi-directional I/O ports with internal pull-up resistors, PD6..PD0. The
Port D output buffers can sink 20 mA. As inputs, Port D pins that are externally pulled
low will source current if the pull-up resistors are activated. The Port D pins are tri-stated
when a reset condition becomes active, even if the clock is not active.
Port D also serves the functions of various special features of the AT90S2313 as listed
on page 58.
RESET Reset input. A low level on this pin for more 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.

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Crystal Oscillator XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier that can
be configured for use as an on-chip oscillator, as shown in Figure 2. Either a quartz
crystal or a ceramic resonator may be used. To drive the device from an external clock
source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in Figure 3.
Figure 2. Oscillator Connections
Note: When using the MCU Oscillator as a clock for an external device, an HC buffer should be
connected as indicated in the figure.
Figure 3. External Clock Drive Configuration
XTAL2
XTAL1
GND
C2
C1
MAX 1 HC BUFFER
HC

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AT90S2313
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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.
Figure 4. The AT90S2313 AVR RISC Architecture
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-register, Y-register and Z-register.
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 4
shows the AT90S2313 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.

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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 mem-
ory can be accessed directly or as the Data Space locations following those of the
register file, $20 - $5F.
The AVR has Harvard architecture – with separate memories and buses for program
and data. The program memory is accessed with a 2-stage pipeline. While one instruc-
tion is being executed, the next instruction is pre-fetched from the program memory.
This concept enables instructions to be executed in every clock cycle. The program
memory is In-System Programmable 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.

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Figure 5. 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.

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General-purpose
Register File
Figure 6 shows the structure of the 32 general-purpose registers in the CPU.
Figure 6. 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, 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, OR and
all other operations between two registers or on a single register apply to the entire reg-
ister file.
As shown in Figure 6, 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.
X-register, Y-register, and Z-
register
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 7.
Figure 7. X, Y and Z Registers
7 0 Addr.
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
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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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, logical and bit functions.
In-System
Programmable Flash
Program Memory
The AT90S2313 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 1,000 write/erase cycles.
The AT90S2313 Program Counter (PC) is 10 bits wide, thus addressing the 1,024 pro-
gram memory addresses.
See page 62 for a detailed description on Flash data downloading. See page 11 for the
different addressing modes.
EEPROM Data Memory The AT90S2313 contains 128 bytes of EEPROM data memory. It is organized as a sep-
arate 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 40, specifying the EEPROM address register, the
EEPROM data register and the EEPROM control register.
For the SPI data downloading, see page 69 for a detailed description.

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SRAM Data Memory Figure 8 shows how the AT90S2313 data memory is organized.
Figure 8. SRAM Organization
The 224 data memory locations address the Register file, I/O memory and the data
SRAM. The first 96 locations address the Register File + I/O Memory, and the next 128
locations address the data SRAM.
The five different addressing modes for the data memory cover: Direct, Indirect with Dis-
placement, Indirect, Indirect with Pre-decrement and Indirect with Post-increment. In the
register file, registers R26 to R31 feature the indirect addressing pointer registers.
The Direct addressing reaches the entire data address space.
The Indirect with Displacement mode features 63 address locations reached from the
base address given by the Y and Z registers.
When using register indirect addressing modes with automatic pre-decrement and post-
increment, the address registers X, Y and Z are used and decremented and
incremented.
The 32 general-purpose working registers, 64 I/O registers and the 128 bytes of data
SRAM in the AT90S2313 are all directly accessible through all these addressing modes.
Register File Data Address Space
R0 $00
R1 $01
R2 $02
……
R29 $1D
R30 $1E
R31 $1F
I/O Registers
$00 $20
$01 $21
$02 $22
……
$3D $5D
$3E $5E
$3F $5F
Internal SRAM
$60
$61
$62
…
$DD
$DE
$DF