MC68HC908GR8A_07 Datasheet, PDF (194/260 Pages) Freescale Semiconductor, Inc – Microcontrollers

Serial Peripheral Interface (SPI) Module
Use this formula to calculate the SPI baud rate:
Baud rate = ^BUSCLK
BD
15.12.3 SPI Data Register
The SPI data register consists of the read-only receive data register and the write-only 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 registers that can contain different values. See Figure 15-2.
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:
Unaffected by reset
Figure 15-16. 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
register read is not the same as the register written.
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
194
Freescale Semiconductor