P89V51RD2 Philips Semiconductors, P89V51RD2 Datasheet - Page 38

• Manufacturer Part Number: P89V51RD2
• Description: 8-bit 80C51 5 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 12964
Product data
Fig 15. Schemes used by the UART to detect ‘given’ and ‘broadcast’ addresses when multiprocessor
communications is enabled
7.5.9 Automatic address recognition
rx_byte(7)
rx_byte(0)
saden(7)
saden(0)
saddr(7)
saddr(0)
saddr(7)
saddr(0)
Automatic Address Recognition is a feature which allows the UART to recognize
certain addresses in the serial bit stream by using hardware to make the
comparisons. This feature saves a great deal of software overhead by eliminating the
need for the software to examine every serial address which passes by the serial
port. This feature is enabled for the UART by setting the SM2 bit in SCON. In the 9 bit
UART modes, mode 2 and mode 3, the Receive Interrupt flag (RI) will be
automatically set when the received byte contains either the ‘Given’ address or the
‘Broadcast' address. The 9 bit mode requires that the 9th information bit is a
indicate that the received information is an address and not data.
Using the Automatic Address Recognition feature allows a master to selectively
communicate with one or more slaves by invoking the Given slave address or
addresses. All of the slaves may be contacted by using the Broadcast address. Two
Special Function Registers are used to define the slave’s address, SADDR, and the
address mask, SADEN. SADEN is used to define which bits in the SADDR are to be
used and which bits are ‘don’t care’. The SADEN mask can be logically ANDed with
the SADDR to create the ‘Given’ address which the master will use for addressing
each of the slaves. Use of the Given address allows multiple slaves to be recognized
while excluding others.
This device uses the methods presented in
‘Broadcast’ address has been received or not.
The following examples will help to show the versatility of this scheme.
logic used by P89LV51RD2 UART to detect 'given address' in received data
logic used by P89LV51RD2 UART to detect 'given address' in received data
rx_byte(7)
rx_byte(0)
saden(7)
saden(0)
.
.
.
.
.
.
Rev. 01 — 01 March 2004
broadcast_address_match
given_address_match
Figure 15
8-bit microcontrollers with 80C51 core
002aaa527
to determine if a ‘Given’ or
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89V51RD2
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