HT46F49E datasheet(19/88 Pages) HOLTEK

19 / 88 page

HT46F46E/HT46F47E/HT46F48E/HT46F49E

Rev. 1.40

July 28, 2009

Read Only Memory, is by its nature a non-volatile form

of memory, with data retention even when its power

supply is removed. By incorporating this kind of data

memory in the device a whole new host of application

possibilities are made available to the designer. The

availability of EEPROM storage allows information such

as product identification numbers, calibration values,

specific user data, system setup data or other product

information to be stored directly within the product

microcontroller.

EEPROM Data Memory

Dependent upon which device is chosen, the EEPROM

Data Memory capacity is either 128

´8 bits or 256´8 bits.

Unlike the Program Memory and RAM Data Memory,

the EEPROM Data Memory is not directly mapped and

is therefore not directly accessible in same way as the

other types of memory. Instead it has to be accessed in-

directly through the EEPROM Control Register.

Device

EEPROM Memory Capacity

Except HT46F49E

128

´8

HT46F49E

256

´8

EEPROM Data Memory Capacity

Accessing the EEPROM Data Memory

The EEPROM Data Memory is accessed using a set of

seven instructions. These instructions control all func-

tions of the EEPROM such as read, write, erase, enable

etc. The internal EEPROM structure is similar to that of a

standard 3-wire EEPROM, for which four pins are used

for transfer of instruction, address and data information.

These are the Chip Select pin, CS, Serial Clock pin, SK,

Data In pin, DI and the Data Out pin, DO. All actions re-

lated to the EEPROM must be conducted through the

EECR register which is located in Bank 1 of the RAM

Data Memory, in which each of these four EEPROM

pins is represented by a bit in the EECR register. By ma-

nipulating these four bits in the EECR register, in accor-

dance with the accompanying timing diagrams, the

microcontroller can communicate with the EEPROM

and carry out the required functions, such as reading

and writing data.

Bit

No.

Label

EEPROM Function

0~3

Not implemented bit, read as

²0²

EEPROM Data Memory select

5SK

Serial Clock: Used to clock data into

and out of the EEPROM

6DI

Data Input: Instructions, address and

data information are written to the

EEPROM on this pin

7DO

Data Output: Data from the

EEPROM is readout with this bit. Will

be in a high-impedance condition if

no data is being read.

EECR Register EEPROM Control Bit Functions

When reading data from the EEPROM, the data will

clocked out on the rising edge of SK and appear on DO.

The DO pin will normally be in a high-impedance condi-

tion unless a READ statement is being executed. When

writing to the EEPROM the data must be presented first

on DI and then clocked in on the rising edge of SK. After

all the instruction, address and data information has

been transmitted, CS should be cleared to

²0² to termi-

nate the instruction transmission. Note that after power

on the EEPROM must be initialised as described.

As indirect addressing is the only way to access the

EECR register, all read and write operations to this reg-

ister must take place using the Indirect Addressing Reg-

ister, IAR1, and the Memory Pointer, MP1. Because the

EECR control register is located in Bank 1 of the RAM

Data Memory at location 40H, the MP1 Memory Pointer

must first be set to the value 40H and the Bank Pointer

set to

²1².

C S

S K

D O

D I

t C D S

t C S S

t C S H

t S K L

t S K H

t D I S

t D I H

t P D 1

t P D 0

V a l i d D a t a

Clocking Data In and Out of the EEPROM

HT46F49E Datasheet(PDF) 19 Page - Holtek Semiconductor Inc

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