MC68HC908GP20 Datasheet, PDF (343/406 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Table 20-4. SPI Master Baud Rate Selection
SPR1 and SPR0
00
01
10
11
Baud Rate Divisor (BD)
2
8
32
128
Use this formula to calculate the SPI baud rate:
Baud rate = ^{C-----G-----M-----O----U-----T--}
2 × BD
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
20.14.3 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 20-2.)
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 20-15. 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.
MC68HC908GP20 — Rev 2.1
Freescale Semiconductor
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