ATPL00B datasheet(20/152 Pages) ATMEL

20 / 152 page

Atmel ATPL00B [datasheet]

43028A-ATPL - 9/12

XDATA occupies a separate address space from Program Memory. Up to 64kbytes of XDATA can be

addressed in the Data Memory space. The CPU generates the internal “read” and “write” signals, RD and WR,

needed during XDATA Memory accesses.

Additionally to these 128 Kbytes of SRAM, there are 384 bytes of internal data memory (IDATA) in the ADD8051C3A

core. This is explained in more detail in 4.3.3 section.

Figure 4-3.

128KB SRAM, XDATA and Program Memory

The program must be uploaded to the SRAM after power up. The source of program must be a non volatile storage unit

(i.e. serial flash). A specific module (boot loader peripheral) has been designed to control the booting of the system after

power up. The boot loader module can also be used to program the non volatile storage unit (serial flash) using a serial

link. The non volatile storage unit must be connected to P5 port pins used for the SPI0 link (see Table 4-1). The serial

link to the boot loader shares pins with the microcontroller Serial Port 0. For more information see boot loader section in

4.3.1

Program Memory

After reset, the CPU begins execution from location 0000H and stack pointer (SP) value is set to 07H.

Interrupt Handling

A fixed location in Program Memory is assigned to each interrupt. The interrupt causes the CPU to jump to that

location, where it begins executing the service routine.

Example: External Interrupt 0, is assigned to location 0003H. If External Interrupt 0 is going to be used, its

service routine must begin at location 0003H. If the interrupt is not going to be used, its service location is

available as general purpose Program Memory.

The interrupt service locations are spaced at 8-byte intervals beginning at 0x0003 (i.e.0x0003 for External

Interrupt0, 0x000B for Timer0, etc.).

If an interrupt service routine is short enough, it can reside entirely within that 8-byte interval. Longer service

routines can use a jump instruction to skip over subsequent interrupt locations, if other interrupts are in use.

Program Memory addresses are always 17 bits wide, even though the actual amount of Program Memory used

may be less than 64kbytes.

XDATA increases downwards

XDATA physical address =

(1FFFF - logical address)

Program Memory

increases upwards

128Kbytes

SRAM

0x00000

XDATA

Program Memory

ATPL00B Datasheet(PDF) 20 Page - ATMEL Corporation