AS8228 datasheet(77/123 Pages) AMSCO

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Data Sheet AS8218 / AS8228

Revision 3.0, 31-May-06

Page 77 of 123

8.6

8051 Microcontroller (MCU)

The MCU is a derivative of the well-known 8051 microcontroller. The MCU block consists of an 8051

compatible microprocessor core, program memory (P_RAM), data memory (X_RAM), squareroot calculation

unit and two UARTs for debugging and communication purposes. The Special Function Registers (SFR) section

enfolds the standard blocks like the 16 bit timer (Timer 0), 128 bytes of internal data memory (I_RAM) and a

serial interface (UART1). Furthermore, a squareroot block and a second serial interface (UART2) are also

provided.

Timer 1, Port 0 to 3 and the UART are not implemented exactly the same as in the original 8051. Instead, the

bus extension (Port 0, 2 on single chip 8051) provides access to on-chip periphery, which comprises a serial

peripheral interface (SPI), a real time clock (RTC), nine general purpose I/Os (MPIO), the LCD driver (LCDD),

the DSP block that interfaces to the analog front end and system control registers (SCT). The MCU block is

configured as Von Neumann architecture with the program memory (P_RAM) section staring from 0000h and

the data memory (X_RAM) and periphery section starting from 8000h up to FFFFh. All 64kB of memory can be

accessed with both, the MOVC instruction (for program fetches and data read) and the MOVX instruction (for

data read/store). The interrupt controller enfolds 7 internal interrupt sources, for having all necessary

peripherals already on chip.

MCU

Inter n al

Inter r u p t So ur ce s

Interrupt

Control

CPU

Clock

Divider

128 bytes

I_RAM

Timer 0

24kB

P_RAM

SQRT

UART2

1kB

X_RAM

UART1

Mclk

RXD

TXD

Boot

Load

LCDD

RTC

SCT

MPIO

DSP

I/Os

SPI

AFE

Serial

EEPROM

Display

rxd2

txd2

Figure 21: MCU block diagram

Legend

CPU ................ 8051 compatible microcontroller core

I_RAM ............. 128 bytes static RAM, range 00h to 7Fh of 8051

X_RAM ............ 1024 bytes static RAM, (extended) memory for data storage

P_RAM ............ 24kB static RAM, primarily for program storage, maybe used also for data

Timer 0............ 16 bit timer (due to 8051 standard)

UART1 ............ serial interface RS232 (due to 8051 standard) with extended baudrate generator

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