HT85F2240 datasheet(38/147 Pages) HOLTEK

38 / 147 page

Rev. 1.10

�8 of 147

�� 1� �01�

A/D Flash 8051 Core Low Pin Count MCU

HT85F2230/HT85F2240

Program Memory Protection

The flash program memory is partitioned into two memory blocks. One is the main memory block

and the other is the ID block. The ID block size is 32 bytes and is used to setup the protected

sectors. This memory protection function is used to protect the Program Memory from improper

Program, Erase or Read operations. The flash program memory is divided into several sectors

according to the memory size. Each sector has a capacity of 1K bytes. The memory protection

function is implemented by register control. If a value, with the exception of 0FFH, is written into

the corresponding control register, the corresponding sector program memory protection function

will be enabled. This program memory sector will then be unable to be programmed, erased or read

by corresponding instructions. In this way, the user can select which block of the flash memory is

to be protected.

Memory Protection Control Bytes

The protection of program code memory is categorised to two types: Security Type 1 and Security

Type 2.

■

Security Type 1

Take the HT85F2240 as an example, its inhibit bytes SECURITY1[0:3] are located at the

address 0x00~0x03 of the ID block page 0. If a value, with the exception of 0FFH, has been

written to SECURITY1[N], this sector can not be programmed, erased or read when in the ICP

mode or when executing the OCDSINSTR instruction in the OCDS mode.

With regard to the IAP program, in the OCDS mode, when using the OCDSINSTR instruction

to execute the IAP program, any sector with a security mechanism can be protected from being

programmed, erased or read. If the IAP program is executed when running the main program, all

sectors with security or not, can be programmed, erased or read.

With regard to the MOVC instruction, in the OCDS mode, when using the OCDSINSTR

instruction to execute the MOVC instruction, any sector with security mechanism can not be

read. When executing the MOVC instruction in the main program, all sectors with security or

not, can be read.

The following table illustrates the protection status in the OCDS/ICP/IAP/MOVC modes when

the SECURITY1[0:3] bytes are written with a value other than 0FFH:

SECURITY1[N]

N=0~3

Program

Erase

Read

Protect

Sector #

Remove

Protection

ICP

N/A(1)

Erase A��

IAP

OCDS(�)

X(�)

X(4)

Erase A��

Main Program

O(�)

Erase A��

OCDS(�)

N/A(�)

X(4)

Erase A��

Main Program

N/A(�)

Erase A��

Note: (1) “N/A” means no path to read ROM code.

(�) “N/A” means witho�t this f�nction

(�) “X” stands for inhibited; “O” stands for enab�ed.

(4) If a read operation is inhibited, reading the Flash will return a fixed Flash code of 00H.

(�) In the OCDS mode� on�� when exec�ting the OCDSINSTR instr�ction wi�� the sectors be

protected.

HT85F2240 Datasheet(PDF) 38 Page - Holtek Semiconductor Inc

HT85F2240 Datasheet(HTML) 38 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL