Philips P89LPC920 User Manual page 61

Philips Semiconductors
UART
Slave 0 SADDR = 1100 0000
SADEN = 1111 1001
Given = 1100 0XX0
Slave 1 SADDR = 1110 0000
SADEN = 1111 1010
Given = 1110 0X0X
Slave 2 SADDR = 1110 0000
SADEN = 1111 1100
Given = 1110 00XX
In the above example the differentiation among the 3 slaves is in the lower 3 address bits. Slave 0 requires that bit 0 = 0 and it
can be uniquely addressed by 1110 0110. Slave 1 requires that bit 1 = 0 and it can be uniquely addressed by 1110 and 0101.
Slave 2 requires that bit 2 = 0 and its unique address is 1110 0011. To select Slaves 0 and 1 and exclude Slave 2 use address
1110 0100, since it is necessary to make bit 2 = 1 to exclude slave 2. The Broadcast Address for each slave is created by taking
the logical OR of SADDR and SADEN. Zeros in this result are treated as don't-cares. In most cases, interpreting the don't-cares
as ones, the broadcast address will be FF hexadecimal. Upon reset SADDR and SADEN are loaded with 0s. 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 UART drivers which do not make use of this feature.
2003 Dec 8
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User's Manual - Preliminary -
P89LPC920/921/922