MC68HC908AS32A Datasheet, PDF (225/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

I/O Registers
16.13.3 SPI Data Register
The SPI data register is the read/write buffer for the receive data register and the transmit data register.
Writing to the SPI data register writes data into the transmit data register. Reading the SPI data register
reads data from the receive data register. The transmit data and receive data registers are separate
buffers that can contain different values. See Figure 16-2.
Address: $0012
Bit 7
6
5
4
3
2
1
Bit 0
Read: R7
R6
R5
R4
R3
R2
R1
R0
Write: T7
T6
T5
T4
T3
T2
T1
T0
Reset:
Indeterminate after reset
Figure 16-14. SPI Data Register (SPDR)
R7–R0/T7–T0 — Receive/Transmit Data Bits
NOTE
Do not use read-modify-write instructions on the SPI data register since the
buffer read is not the same as the buffer written.
MC68HC908AS32A Data Sheet, Rev. 2.0
Freescale Semiconductor
225