STC89LE53RC datasheet(121/165 Pages) STC

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In the above example the differentiation among the 3 slaves is in the lower 3 address bits.Slave 0 requires that

bit0 = 0 and it can be uniquely addressed by 11100110. Slave 1 requires that bit 1=0 and it can be uniquely

addressed by 11100101. Slave 2 requires that bit 2=0 and its unique address is 11100011. To select Salve 0 and 1

and exclude Slave 2, use address 11100100, since it is necessary to make bit2=1 to exclude Slave 2.

The Broadcast Address for each slave is created by taking the logic OR of SADDR and SADEN. Zeros in this

result are trended as don’t cares. In most cares, interpreting the don’t cares as ones, the broadcast address will be

FF hexadecimal.

Upon reset SADDR and SADEN are loaded with “0”s. This produces a given address of all “don’t cares as well

as a Broadcast address of all “don’t cares”. This effectively disables the Automatic Addressing mode and allows

the microcontroller to use standard 80C51-type UART drivers which do not make use of this feature.

Example: write an program that continually transmits characters from a transmit buffer. If incoming characters

are detected on the serial port, store them in the receive buffer starting at internal RAM location 50H. Assume that

the STC89xx MCU serial port has already been initialized in mode 1.

Solution:

ORG

0030H

MOV

R0,

#30H

;pointer for tx buffer

MOV

R1,

#50H

;pointer for rx buffer

LOOP:

RI,

RECEIVE

;character received?

;yes: process it

TI,

;previous character transmitted ?

;yes: process it

SJMP

LOOP

;no: continue checking

TX:

MOV

@R0

;get character from tx buffer

MOV

;put parity bit in C

CLR

;change to odd parity

MOV

ACC.7, C

;add to character code

CLR

;clear transmit flag

MOV

SBUF,

;send character

CLR

ACC.7

;strip off parity bit

INC

;point to next character in buffer

CJNE

R0,

#50H,

LOOP

;end of buffer?

;no: continue

MOV

R0,

#30H

;yes: recycle

SJMP

LOOP

;continue checking

RX:

CLR

;clear receive flag

MOV

SBUF

;read character into A

MOV

;for odd parity in A, P should be set

CPL

;complementing correctly indicates "error"

CLR

ACC.7

;strip off parity

MOV

@R1,

;store received character in buffer

INC

;point to next location in buffer

SJMP

LOOP

;continue checking

END

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