MC68HC08AS32A Datasheet, PDF (238/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Serial Peripheral Interface (SPI)
Table 15-5. SPI Master Baud Rate Selection
SPR1: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),
see Section 5. Clock Generator Module (CGM).
BD = baud rate divisor
15.13.3 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 15-3.
NOTE:
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
Do not use read-modify-write instructions on the SPI data register since the buffer
read is not the same as the buffer written.
Data Sheet
238
Serial Peripheral Interface (SPI)
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Go to: www.freescale.com
MC68HC08AS32A — Rev. 1
MOTOROLA