Silan

Semiconductors

SC8521

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.3

2002.03.01

6

3. Single system

SN0 should be connected to one of the drivelines or ground.

The bank that will be selected is equal to drive line number to which SN0 is connected. When connected to

ground the number will be 7. This achieved by loading the bank select flip-flops BS0 to BS2 with the contents of

C5 to C7 of the control timer when sense line SN0 is at logic 0. In this way it is possible to use two different

systems in one transmitter by using a side switch. With this option SN0 cannot be used to connect keys, so the

maximum number of keys will be lower (49 keys with 20-pin IC).

4. Multi system

The bank is selected by key for maximum 8 different systems (e.g. TV, VCR, CD, etc.), any key is flexible for

bank selection. When a user inserts a new battery, the default bank is always in bank 7. If only bank 7 is used,

then maximum number of key can be 56 keys for a 20-pin IC

5. ROM

Logic 1

Logic 0

A schematic diagram of the ROM is illustrated. The ROM is divided into 8 banks of 2

× 64 bytes. Bank selection

is performed using flip-flops BS0 to BS2 that are the 3 highest bits of the address. With the ‘single system’ these

bits are loaded from the 3 MSBs of the scan control when SN0 = 0. At power-on the bank select flip-flops will be in

an arbitrary state.

When a key was activated, the key number is stored in the 6-bit key register. This register forms the lower bits of

the ROM address. For each command the ROM will be accessed twice. This gives 16 bits in total (M0L to M7L

and M0H to M7H). The bits are described in Table 2.

Table2 ROM bit description

Bits

Function

M0LtoM5L

Command bits 0to5

M6L

Field bit. This bit indicates whether command codes 0 to 63 are used (filed bit is at logic 1)

or command codes 64 to 127 are used (filed bit is at logic 0).

M7L

Inhibit bit. When this bit is at logic 1 no transmission will take place. When this bit is at

logic 0 the appropriate code word will be transmitted.

M0H to M4H

System bits 0 to 4

M5H to M7H

Bank select. Will be stored in BS0 to BS2 when the ‘multi-system’ option is selected. With

single system bits M5H to M7H are don’t care.