P89V51RD2 Philips Semiconductors, P89V51RD2 Datasheet - Page 39

• 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
7.6.1 SPI features
7.6 Serial peripheral interface
Table 26:
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:
Table 27:
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 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.
Slave 0
Slave 1
Slave 0
Slave 1
Slave 2
•
•
Master or slave operation
10 MHz bit frequency (max)
SADDR = 1100 0000
SADEN = 1111 1101
Given =
SADDR = 1100 0000
SADEN = 1111 1110
Given =
SADDR = 1110 0000
SADEN = 1111 1001
Given =
SADDR = 1110 0000
SADEN = 1111 1010
Given =
SADDR = 1110 0000
SADEN = 1111 1100
Given =
Slaves 0 and 1 scheme examples
Slaves 0, 1 and 2 scheme examples
Rev. 01 — 01 March 2004
1100 00X0
1100 000X
1110 0XX0
1110 0X0X
1110 00XX
8-bit microcontrollers with 80C51 core
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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