PCA8521 datasheet(6/20 Pages) PHILIPS

6 / 20 page

1999 Jun 15

Philips Semiconductors

Product speciﬁcation

Infrared remote control transmitter RC5

PCA8521

FUNCTIONAL DESCRIPTION

Key numbering for the matrix is given in Tables 1 and 2.

Table 1

Key numbering for 16-pin package

Table 2

Key numbering for 20-pin package

DRIVER

LINES

SENSE LINES

SN0

SN1

SN2

SN3

SN4

SN5

DR0

012345

DR1

DR2

DR3

DR4

DRIVER

LINES

SENSE LINES

SN0

SN1

SN2

SN3

SN4

SN5

SN6

SN7

DR0

01234567

DR1

DR2

DR3

DR4

DR5

DR6

When the keys have been scanned the key-number of the

activated key serves as the address of the ROM to obtain

the required code-word. When a 16-pin IC is used the

following sense lines and driver lines will not be connected;

SN6, SN7, DR5 and DR6. Consequently, key numbers 6,

7, 14, 15, 22, 23, 30, 31, 38, 39 and 40 to 55 will not be

addressed.

The ROM contains 8 banks of 64 code-words. Thus for

each key a maximum of 8 different code-words may be

generated. With multi-system use, 8 different systems

(e.g. TV, VCR, tuner, CD etc.) may be selected. Apart from

the system bits the command bits may also be different in

different banks (true multi-function keys). Selection can be

performed using the keys. For each key three bank select

bits are present that determine which bank will be selected

for the next key.

For each key an ‘inhibit’ bit is also present. When this bit is

at logic 1 at an address in a given bank, and when the

corresponding key is pressed (when this bank has been

selected) no transmission will take place.

A single system option is available however, whereby

instead of keys a jumper wire and/or a switch may be used

for bank selection. Using this option it is possible to

program different transmitter models in one IC and select

the required bank by means of a jumper wire. Instead of a

jumper wire a side-switch may also be used to change the

generated code temporarily (select different bank) to

obtain multi-function keys. With this option the jumper

wires or switch must be connected between sense line

SN0 and one of the drive lines DR0 to DR6 or ground. This

means that SN0 cannot be used to connect keys and the

maximum number of keys will be 25 keys for a 16-pin

package and 49 keys for a 20-pin package.

It is not possible to use a combination of jumper wires and

selection keys for bank selection in one unit.

The output of the ROM is loaded into a shift register that

provides the input bits for the pulse generator. This pulse

generator drives the output pin.

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