Sailor RT2047 Service Manual download pdf (Page 54)

2 CIRCUIT DESCRIPTION RT2047 DSC - PART II

When the radio is switched on the dividing figure corresponding to the first figure in the selcall number

is put on port A on the µC which is connected to the input of U18-6. If the correct tone is received the output

of the comparator U15/1-6 goes low. This output is connected to the µC’s INT-pin. When the tone

disappears again the µC will put out the dividing figure corresponding to the next figure in the selcall

number. If all five tones are received correctly then the µC will send a message on the serial interface to

the keyboard unit, turn on the selcall relay RE2-9 (on the filter unit), and send out an alarm tone from PC1

via the volume control and power amp. to the loudspeaker. The alarm tone lasts for 10 seconds after an

individual call and after an all call it lasts until the selcall is reset. If the SELCALL TEST button is activated

the alarm circuits and indicators will be tested.

2.6.13 THE EEPROM

The EEPROM contains an address/opcode register, a data I/O register, a memory array, an internal high

voltage generator (V

) and some decoding logic. The Serial Data Clock (CK) is fed from PC7 on the µC

and all communication starts with the µC setting PC5 thus enabling the Chip Select (CS) on the eeprom

(U8-6). Instructions to U8-6 consists of a dummy 1, a 2 bit opcode, an 8 bit address and for some

instructions also a 16 bit data word. When the opcode is 00 the 2 first bits in the address serve as an

extended opcode.

INSTRUCTION SET FOR THE EEPROM (NMC93C56):

,QVWUXFWLRQ 2S $ GGUHVV 'DWD &RPPHQW

FRGH

READ 10 A7-A0 Reads data at specified address

EWEN 0 11XXXXXX

Write enable, must precede all

programming modes

ERASE 11 A7-A0 Erase register A7-A0

ERAL 0 10XXXXXX Erase all registers

WRITE 1 A7-A0 D15-D0 Writes reg if address unprotected

WRAL 0 01XXXXXX D15-D0

Writes all registers. Valid only when

Protect Reg is cleared

EWDS 0 00XXXXXX Disables all programming instructions

READ:

After a Read instruction is received, the instruction and address are decoded, followed by data transfer

from the selected memory register. A dummy 0 precedes the 16-bit data output string. Output data

changes are initiated by a low to high trasition of the SK clock.

WRITE:

The Write operation is followed by 16 bits of data to be written to the specified address. CS must then be

brought low before the next rising edge of the SK clock to initiate the self-timed programming cycle. D0

indicates the ready state ( 1/0 => ready/busy ) the chip is ready for another instruction.

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Sailor RT2047 Service Manual Page 54