ATR0621P1 Datasheet, PDF (4/14 Pages) ATMEL Corporation – GPS Baseband Processor

2. Architectural Overview
2.1 Description
The ATR0621P1 architecture consists of two main buses, the Advanced System Bus (ASB) and
the Advanced Peripheral Bus (APB). The ASB is designed for maximum performance. It inter-
faces the processor with the on-chip 32-bit memories and the external memories and devices by
means of the External Bus Interface (EBI). The APB is designed for accesses to on-chip periph-
erals and is optimized for low power consumption. The AMBA^™ Bridge provides an interface
between the ASB and the APB.
An on-chip Peripheral Data Controller (PDC2) transfers data between the on-chip USARTs/SPI
and the on-chip and off-chip memories without processor intervention. Most importantly, the
PDC2 removes the processor interrupt handling overhead and significantly reduces the number
of clock cycles required for a data transfer. It can transfer up to 64K contiguous bytes without
reprogramming the starting address. As a result, the performance of the microcontroller is
increased and the power consumption reduced.
The ATR0621P1 peripherals are designed to be easily programmable with a minimum number
of instructions. Each peripheral has a 16 Kbyte address space allocated in the upper 3 Mbyte of
the 4 Gbyte address space. (Except for the interrupt controller, which has 4 Kbyte address
space.) The peripheral base address is the lowest address of its memory space. The peripheral
register set is composed of control, mode, data, status, and interrupt registers.
To maximize the efficiency of bit manipulation, frequently written registers are mapped into three
memory locations. The first address is used to set the individual register bits, the second resets
the bits, and the third address reads the value stored in the register. A bit can be set or reset by
writing a “1” to the corresponding position at the appropriate address. Writing a “0” has no effect.
Individual bits can thus be modified without having to use costly read-modify-write and complex
bit-manipulation instructions.
All of the external signals of the on-chip peripherals are under the control of the Parallel I/O
(PIO2) Controller. The PIO2 Controller can be programmed to insert an input filter on each pin or
generate an interrupt on a signal change. After reset, the user must carefully program the PIO2
Controller in order to define which peripheral signals are connected with off-chip logic.
The ARM7TDMI processor operates in little-endian mode on the ATR0621P1 GPS Baseband.
The processor's internal architecture and the ARM and Thumb instruction sets are described in
the ARM7TDMI datasheet.
The ARM standard In-Circuit Emulation debug interface is supported via the JTAG/ICE port of
the ATR0621P1.
Features of the ROM firmware are described in software documentation available from u-blox
AG, Switzerland.
4 ATR0621P1
4975BS–GPS–05/08