ST6365 datasheet(13/84 Pages) STMICROELECTRONICS

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ST6365, ST6375, ST6385 ST6367, ST6377, ST6387

MEMORY SPACES (Cont’d)

1.3.4

Data

RAM/EEPROM/OSD

RAM

Addressing

In all members of the ST638x family 64 bytes of

data RAM are directly addressable in the data

space from 80h to BFh addresses. The additional

192 bytes of RAM, the 384 bytes of EEPROM, and

the OSD RAM can be addressed using the banks

of 64 bytes located between addresses 00h and

3Fh. The selection of the bank is done by pro-

gramming the Data RAM Bank Register (DRBR)

located at the E8h address of the Data Space. In

this way each bank of RAM, EEPROM or OSD

RAM can select 64 bytes at a time. No more than

one bank should be set at a time.

Data RAM Bank Register (DRBR)

Address: E8h - Write only

Reset Value: XXh

DRBR7,DRBR1,DRBR0. These bits select the

EEPROM pages.

DRBR6, DRBR5. Each of these bits, when set, will

select one OSD RAM register page.

DRBR4,DRBR3,DRBR2. Each of these bits, when

set, will select oneRAM page.

This register is undefined after reset.

Table 5 summarizes how to set the Data RAM

Bank Register in order to select the various banks

or pages.

Caution: This register contains at least one write

only bit. Single bit instructions (SET, RES, INC

and DEC) should not be used.

Note: Care is required when handling the DRBR

as it is write only. For this reason, it is not allowed

to change the DRBR contents while executing in-

terrupts drivers, as the driver cannot save and

than restore its previous content. If it is impossible

to avoid the writing of this register in interrupts

drivers, an image of this register must be saved in

a RAM location, and each time the program writes

the DRBR it writes also the image register. The im-

age register must be written first, so if an interrupt

occurs between the two instructions the DRBR is

not affected.

Table 5. Data RAM Bank Register Set-up

DRBR

DRBR Value

Selection

Hex.

Binary

01h

0000 0001

EEPROM Page 0

02h

0000 0010

EEPROM Page 1

03h

0000 0011

EEPROM Page 2

81h

1000 0001

EEPROM Page 3

82h

1000 0010

EEPROM Page 4

83h

1000 0011

EEPROM Page 5

04h

0000 0100

RAM Page 2

08h

0000 1000

RAM Page 3

10h

0001 0000

RAM Page 4

20h

0010 0000

OSD Page 5

40h

0100 0000

OSD Page 6

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