p89cv51rb2 NXP Semiconductors, p89cv51rb2 Datasheet - Page 38

• Manufacturer Part Number: p89cv51rb2
• Description: P89cv51rb2/rc2/rd2 8-bit 80c51 5 V Low Power 64 Kb Flash Microcontroller With 1 Kb Ram, Spi, 6-clock Cpu With 6/12-clock Peripherals
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89CV51RB2_RC2_RD2_1
Product data sheet
Example 1, slave 0:
Example 2, slave 1:
In the above example SADDR is the same and the SADEN data is used to differentiate
between the two slaves. Slave 0 requires a 0 in bit 0 and it ignores bit 1. Slave 1 requires
a 0 in bit 1 and bit 0 is ignored. A unique address for slave 0 would be 1100 0010 since
slave 1 requires a 0 in bit 1. A unique address for slave 1 would be 1100 0001 since a 1 in
bit 0 will exclude slave 0. Both slaves can be selected at the same time by an address
which has bit 0 = 0 (for slave 0) and bit 1 = 0 (for slave 1). Thus, both could be addressed
with 1100 0000.
In a more complex system the following could be used to select slaves 1 and 2 while
excluding slave 0.
Example 1, slave 0:
SADDR = 1100 0000
--------------------------------------------------- -
Example 2, slave 1:
SADDR = 1110 0000
--------------------------------------------------- -
Example 3, slave 2:
SADDR = 1100 0000
--------------------------------------------------- -
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 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 FFH. 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.
SADEN = 1111 1001
SADEN = 1111 1010
SADEN = 1111 1100
SADDR = 1100 0000
--------------------------------------------------- -
SADDR = 1100 0000
--------------------------------------------------- -
SADEN = 1111 1101
SADEN = 1111 1110
Given = 1100 0XX0
Given = 1110 0X0X
Given = 1100 00XX
Given = 1100 00X0
Given = 1100 000X
Rev. 01 — 5 October 2007
P89CV51RB2/RC2/RD2
80C51 with 1 kB RAM, SPI
© NXP B.V. 2007. All rights reserved.
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