Motorola MC68HC908MR32 사용자 설명서
Serial Peripheral Interface Module (SPI)
I/O Registers
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
Advance Information
MOTOROLA
Serial Peripheral Interface Module (SPI)
275
Use this formula to calculate the SPI baud rate:
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
BD = baud rate divisor
13.13.3 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
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
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.
the register read is not the same as the register written.
Baud rate
CGMOUT
2
BD
×
--------------------------
=
Address: $0046
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 13-15. SPI Data Register (SPDR)