AT91M55800A Datasheet, PDF (9/227 Pages) ATMEL Corporation – ARM Thumb Microcontrollers

Architectural
Overview
Memory
Peripherals
System Peripherals
1745B–ATARM–04/02
AT91M55800A
The AT91M55800A microcontroller integrates an ARM7TDMI with its embedded ICE
interface, memories and peripherals. Its architecture consists of two main buses, the
Advanced System Bus (ASB) and the Advanced Peripheral Bus (APB). Designed for
maximum performance and controlled by the memory controller, the ASB interfaces the
ARM7TDMI processor with the on-chip 32-bit memories, the External Bus Interface
(EBI) and the AMBA^™ Bridge. The AMBA Bridge drives the APB, which is designed for
accesses to on-chip peripherals and optimized for low power consumption.
The AT91M55800A microcontroller implements the ICE port of the ARM7TDMI proces-
sor on dedicated pins, offering a complete, low cost and easy-to-use debug solution for
target debugging.
The AT91M55800A microcontroller embeds 8K bytes of internal SRAM. The internal
memory is directly connected to the 32-bit data bus and is single-cycle accessible.
The AT91M55800A microcontroller features an External Bus Interface (EBI), which
enables connection of external memories and application-specific peripherals. The EBI
supports 8- or 16-bit devices and can use two 8-bit devices to emulate a single 16-bit
device. The EBI implements the early read protocol, enabling faster memory accesses
than standard memory interfaces.
The AT91M55800A microcontroller integrates several peripherals, which are classified
as system or user peripherals. All on-chip peripherals are 32-bit accessible by the
AMBA Bridge, and can be programmed with a minimum number of instructions. The
peripheral register set is composed of control, mode, data, status and enable/dis-
able/status registers.
An on-chip, 8-channel Peripheral Data Controller (PDC) transfers data between the on-
chip USARTs/SPI and the on and off-chip memories without processor intervention.
One PDC channel is connected to the receiving channel and one to the transmitting
channel of each USART and of the SPI.
Most importantly, the PDC removes the processor interrupt handling overhead and sig-
nificantly reduces the number of clock cycles required for a data transfer. It can transfer
up to 64K contiguous bytes. As a result, the performance of the microcontroller is
increased and the power consumption reduced.
The External Bus Interface (EBI) controls the external memory and peripheral devices
via an 8- or 16-bit data bus and is programmed through the APB. Each chip select line
has its own programming register.
The Advanced Power Management Controller (APMC) optimizes power consumption of
the product by controlling the clocking elements such as the oscillators and the PLL,
system and user peripheral clocks, and the power supplies.
The Advanced Interrupt Controller (AIC) controls the internal interrupt sources from the
internal peripherals and the eight external interrupt lines (including the FIQ), to provide
an interrupt and/or fast interrupt request to the ARM7TDMI. It integrates an 8-level prior-
ity controller and, using the Auto-vectoring feature, reduces the interrupt latency time.
The Real-time Clock (RTC) peripheral is designed for very low power consumption, and
combines a complete time-of-day clock with alarm and a two-hundred year Gregorian
calendar, complemented by a programmable periodic interrupt.
The Parallel Input/Output Controllers (PIOA and PIOB) control the 58 I/O lines. They
enable the user to select specific pins for on-chip peripheral input/output functions, and
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