ST6369 datasheet(17/71 Pages) STMICROELECTRONICS

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DRBR

Data RAM

Bank Register

(E8H, Write Only)

D7 D6 D5 D4 D3 D2 D1 D0

DRBR0

DRBR1

DRBR2

DRBR3

DRBR4

DRBR5

DRBR6

DRBR7

Figure 16. Data RAM Bank Register

MEMORY SPACES (Continued)

Data RAM/EEPROM

In the ST6369 64 bytes of data RAM are directly ad-

dressable in the data space from 80H to BFH ad-

dresses. The additional 192 bytes of RAM, the 384

bytes of EEPROM 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 can select

64 bytes at a time. No more than one bank should

be set at a time.

DRBR7,DRBR1,DRBR0. These bits select the

EEPROM page s.

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

set, will select one RAM 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.

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 inter-

rupts 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 driv-

ers, 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 image register must be written first, so if an in-

terrupt occurs between the two instructions the

DRBR is not affected.

EEPROM Description

The data space of ST6369 family from 00H to 3FH

is paged as described in Table 5. 384 bytes of

EEPROM located in six pages of 64 bytes (pages

0,1,2,3,4 and 5, see Table 5).

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

Table 5. Data RAM Bank Register Set-up

ST6369

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