mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 226

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Serial Peripheral Interface Module (SPI)
Use this formula to calculate the SPI baud rate:
where:
CGMOUT = base clock output of the clock generator module (CGM)
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
R7–R0/T7–T0 — Receive/Transmit Data Bits
226
Address:
Do not use read-modify-write instructions on the SPI data register since the
register read is not the same as the register written.
Reset:
Read:
Write:
SPR1 and SPR0
$0012
Bit 7
R7
T7
00
01
10
11
Baud rate
Table 13-4. SPI Master Baud Rate Selection
Figure 13-15. SPI Data Register (SPDR)
MC68HC908AP A-Family Data Sheet, Rev. 3
R6
T6
6
=
CGMOUT
------------------------- -
2 BD
R5
T5
5
×
NOTE
Unaffected by reset
R4
T4
4
Baud Rate Divisor (BD)
Figure
R3
T3
3
128
32
13-2.)
2
8
R2
T2
2
R1
T1
1
Freescale Semiconductor
Bit 0
R0
T0