Specifications

98
3706C–MICRO–2/11
AT89LP3240/6440
In a more complex system, the following could be used to select slaves 1 and 2 while excluding
slave 0:
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 s elect 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 logic OR of SADDR and SADEN.
Zeros in this result are trended as don’t cares. In most cases, interpreting the don’t care
s as
ones, the broadcast address will be FF hexadecimal.
Upon reset SADDR (SFR address 0A9H) and SADEN (SFR address 0B9H) are loaded with
“0”s. 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 microcon-
troller to use standard 80C51-type UART drivers which do not make use of this feature.
17. Enhanced Serial Peripheral Interface
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer b etween the
AT89LP3240/6440 and peripheral devices or between multiple AT89LP3240/6440 devices,
including multiple masters and slaves on a single bus. The SPI includes the following features:
•Full-duplex, 3-wire or 4-wire Synchronous Data Tr ansfer
•M
aster or Slave Operation
•Maximum Bit Frequency = f
OSC
/4
•LSB First or MSB First Data Transfer
•Four Programmable Bit Rates or Timer 1-based Baud Generation (Master Mode)
•End of Transmission Interrupt Flag
• Write Collision Flag Protection
•Double-buffered Receive and Transmit
•Transmit Buffer Empty Interrupt Flag
• Mode Fault (Master Collision) Detection and Interrupt
•Wake up from Idle Mode
A block diagram of the SPI is
shown below in Figure 17-1.