T89C51SND1-ROTIL datasheet(22/60 Pages) ATMEL

22 / 60 page

T8xC51SND1

Rev. D – 15-Nov-01

8. In System & In Application Programming

8.1 Introduction

As described in the section “Program/Code Memory” of the T8xC51SND1 design guide,

The T89C51SND1 implements a 4 Kbytes FLASH boot memory. This boot memory is

delivered programmed with a standard boot loader software allowing In System Pro-

gramming (ISP). It also contains some Application Programming Interface routines

named API routines allowing In Application Programming (IAP) by using user’s own

boot loader.

8.2 In System Programming

The ISP boot process is divided in two different processes: the hardware and software

boot process detailed in the following sections.

8.3.1 Hardware Boot Process

As detailed in Figure 8 there are two hardware conditions that allow user executing the

boot loader: the hardware and the programmed conditions.

Hardware condition

The hardware condition is based on the ISP# pin. When driving this pin to low level, the

chip reset forces the execution of the boot loader software.

The hardware condition takes precedence on the programmed condition and always

allows in system recovery when user’s memory has been corrupted.

Programmed Condition

The programmed condition is based on the Boot Loader Jump Bit (BLJB) in the hard-

ware security bytes (HSB). When this bit is programmed (by hardware or software

programming mode), the chip reset forces the execution of the boot loader software.

8.4.2 Software Boot Process

Whatever the physical medium may be, the boot loader software always starts execu-

tion by testing FCON to know if execution comes from hardware or programmed

condition. If it is from hardware condition, the Atmel’s boot loader is executed. If it is

from programmed condition, the Software Boot Vector (SBV) is used to build a 16-bit

address, SBV content being the MSB and the LSB being 00h. If this address is valid (<

F000h), jump is done to this address to execute user’s boot loader. Otherwise jump is

done to the Atmel’s boot loader. This implies that user’s boot loader does not execute

any code mapped from F000h to FFFFh.

T89C51SND1-ROTIL Datasheet(PDF) 22 Page - ATMEL Corporation