AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 65

• Manufacturer Part Number: AT89C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 2
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

16.3
16.3.1
4235K–8051–05/08
Functional Description
Operating Modes
Figure 16-2
Figure 16-2. SPI Module Block Diagram
The Serial Peripheral Interface can be configured in one of the two modes: Master mode or
Slave mode. The configuration and initialization of the SPI Module is made through one register:
Once the SPI is configured, the data exchange is made using:
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and
received (shifted in serially). A serial clock line (SCK) synchronizes shifting and sampling on the
two serial data lines (MOSI and MISO). A Slave Select line (SS) allows individual selection of a
Slave SPI device; Slave devices that are not selected do not interfere with SPI bus activities.
When the Master device transmits data to the Slave device via the MOSI line, the Slave device
responds by sending data to the Master device via the MISO line. This implies full-duplex trans-
mission with both data out and data in synchronized with the same clock (Figure 16-3).
• The Serial Peripheral Control register (SPCON)
• SPCON
• The Serial Peripheral STAtus register (SPSTA)
• The Serial Peripheral DATa register (SPDAT)
SPI Interrupt Request
shows a detailed structure of the SPI Module.
Clock
Divider
FCLK PERIPH
SPR2
/128
/16
/32
/64
SPEN
/8
/4
Clock
Select
SSDIS
MSTR
SPIF
Receive Data Register
CPOL
7
WCOL
Shift Register
Internal Bus
6
SPI
Control
CPHA
5
4
3
SPR1
-
2
Clock
Logic
SPCON
1
AT89C51RD2/ED2
SPDAT
MODF
0
SPR0
-
M
Pin
Control
Logic
S
-
-
SPSTA
-
8-bit bus
1-bit signal
MOSI
MISO
SCK
SS
65