Serial peripheral data register (spdat) – Rainbow Electronics AT89C5122 User Manual
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146
AT8xC5122/23
4202E–SCR–06/06
Serial Peripheral DATa Register
(SPDAT)
The Serial Peripheral Data Register (Table 87) is a read/write buffer for the receive data
register. 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.
Reset Value = XXXX XXXXb
Table 87. Serial Peripheral Data Register - SPDAT (C5h)
7
6
5
4
3
2
1
0
R7
R6
R5
R4
R3
R2
R1
R0
Bit Number
Bit
Mnemonic Description
7-0
R7:0
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 transmission is on-going:
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