AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 71

• 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

16.3.5.3
4235K–8051–05/08
Serial Peripheral DATa Register (SPDAT)
Reset Value = 00X0 XXXXb
Not Bit addressable
The Serial Peripheral Data Register
ter. A write to SPDAT places data directly into the shift register. No transmit buffer is available in
this model.
A Read of the SPDAT returns the value located in the receive buffer and not the content of the
shift register.
Table 16-5.
SPDAT - Serial Peripheral Data Register (0C5H)
Reset Value = Indeterminate
R7:R0: Receive data bits
SPCON, SPSTA and SPDAT registers may be read and written at any time while there is no on-
going exchange. However, special care should be taken when writing to them while a transmis-
sion is on-going:
Bit Number
• Do not change SPR2, SPR1 and SPR0
• Do not change CPHA and CPOL
• Do not change MSTR
• Clearing SPEN would immediately disable the peripheral
• Writing to the SPDAT will cause an overflow.
R7
5
4
3
2
1
0
7
Mnemonic
SSERR
SPDAT Register
MODF
Bit
R6
-
-
-
-
6
Description
Synchronous Serial Slave Error Flag
Set by hardware when SS is de-asserted before the end of a received data.
Cleared by disabling the SPI (clearing SPEN bit in SPCON).
Mode Fault
Cleared by hardware to indicate that the SS pin is at appropriate logic level, or has been
approved by a clearing sequence.
Set by hardware to indicate that the SS pin is at inappropriate logic level.
Reserved
The value read from this bit is indeterminate. Do not set this bit
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
R5
5
(Table
R4
4
16-5) is a read/write buffer for the receive data regis-
R3
3
AT89C51RD2/ED2
R2
2
R1
1
R0
0
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