MPC89L53AF 参数 Datasheet PDF下载

SM2:

Enable the

automatic address recognition

feature in mode 2 and 3. If

SM2=1, RI

will not be set

unless the received 9th data bit is 1, indicating an address, and the received byte is a Given or

Broadcast address. In mode1, if SM2=1 then RI will not be set unless a valid stop Bit was received,

and the received byte is a Given or Broadcast address.

REN:

Enable the serial port reception.

1

:= enable

0

:= disable

TB8:

The 9th data bit, which will be transmitted in Mode 2 and Mode 3.

RB8:

In mode 2 and 3, the received 9th data bit will go into this bit.

TI:

Transmit interrupt flag. After a transmit has been finished, the hardware will set this bit.

RI:

Receive interrupt flag. After reception has been finished, the hardware will set this bit.

SFR:

SBUF

(Serial

port Buffer register):

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

(data to be transmitted or received data)

Automatic Address Recognition

There is an extra feature makes the device convenient to act as a master, which

communicates to multiple slaves simultaneously. It is really

Automatic Address Recognition.

There are two SFR

SADDR

and

SADEN

implemented in the device. The user can read or

write both of them. Finally, the hardware will make use of these two SFR to “generate” a

“compared byte”. The formula specifies as following.

Bit[

i

] of

Compared Byte =

(SADEN[

i

] == 1

)?

SADDR[

i

]

:

x

For example:

Set

SADDR

= 11000000b

Set

SADEN

= 11111101b

The achieved “Compared Byte” will be “110000x0”

For another example:

Set

SADDR

= 11100000b

Set

SADEN

= 11111010b

The achieved “Compared Byte” will be “11100x0x”

(x means don’t care)

After the generic “Compared Byte” has been worked out, the MPC89x53A will make use of this

byte to determine how to set the bit

RI

in SFR

SCON.

Normally, an UART will set bit

RI

whenever it has done a byte reception; but for the UART in the

MPC89x53A, if the bit

SM2

is set, it will set

RI

according to the following formula.

RI

=

(SM2 ==

1)

&& (SBUF ==

Compared Byte)

&& (RB8 ==

1)

MEGAWIN

MPC89x53A Data Sheet

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