AT89LP4052 Atmel Corporation, AT89LP4052 Datasheet - Page 42

• Manufacturer Part Number: AT89LP4052
• Manufacturer: Atmel Corporation

Specifications of AT89LP4052

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 15
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.25
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 2
• Isp: SPI
• Watchdog: Yes

19. Serial Peripheral Interface
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AT89LP2052/LP4052
In a more complex system the following could be used to select slaves 1 and 2 while excluding
slave 0:
Slave 0
Slave 1
Slave 2
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 logic 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 (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.
The serial peripheral interface (SPI) allows high-speed synchronous data transfer between the
AT89LP2052/LP4052 and peripheral devices or between multiple AT89LP2052/LP4052
devices. The AT89LP2052/LP4052 SPI features include the following:
• Full-duplex, 3-wire Synchronous Data Transfer
• Master or Slave Operation
• Maximum Bit Frequency = f/4
• LSB First or MSB First Data Transfer
• Four Programmable Bit Rates in Master Mode
• End of Transmission Interrupt Flag
• Write Collision Flag Protection
• Double-buffered Receive
• Double-buffered Transmit (Enhanced Mode Only)
• Wake up from Idle Mode (Slave Mode Only)
SADDR = 1100 0000
SADEN = 1111 1001
Given = 1100 0XX0
SADDR = 1110 0000
SADEN = 1111 1010
Given = 1110 0X0X
SADDR = 1110 0000
SADEN = 1111 1100
Given = 1110 00XX
3547J–MICRO–10/09