MC68HC708XL36 FREESCALE [Freescale Semiconductor, Inc], MC68HC708XL36 Datasheet - Page 227

• Manufacturer Part Number: MC68HC708XL36
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

CGND (Clock
Ground)
27-spi_c
MOTOROLA
NOTE:
state of the MODFEN control bit. However, the MODFEN bit can still
prevent the state of the SS from creating a MODF error. (See
and Control Register
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a
high-impedance state. The slave SPI ignores all incoming SPSCK
clocks, even if it was already in the middle of a transmission.
When an SPI is configured as a master, the SS input can be used in
conjunction with the MODF flag to prevent multiple masters from driving
MOSI and SPSCK. (See
of the SS pin to set the MODF flag, the MODFEN bit in the SPSCK
register must be set. If the MODFEN bit is low for an SPI master, the SS
pin can be used as a general-purpose I/O under the control of the data
direction register of the shared I/O port. With MODFEN high, it is an
input-only pin to the SPI regardless of the state of the data direction
register of the shared I/O port.
The CPU can always read the state of the SS pin by configuring the
appropriate pin as an input and reading the port data register. (See
Table
CGND is the ground return for the serial clock pin, SPSCK, and the
ground for the port output buffers. To reduce the ground return path loop
and minimize radio frequency (RF) emissions, connect the ground pin of
the slave to the CGND pin of the master.
SPE
1. X = don’t care
0
1
1
1
Freescale Semiconductor, Inc.
For More Information On This Product,
4.)
SPMSTR
X
0
1
1
(1)
Go to: www.freescale.com
MODFEN
Table 4. SPI Configuration
X
X
0
1
SPI
on page 230.)
Mode Fault Error
Master without MODF
SPI Configuration
Master with MODF
Not Enabled
Slave
on page 218.) For the state
General-purpose I/O;
General-purpose I/O;
State of SS Logic
SS ignored by SPI
SS ignored by SPI
Input-only to SPI
Input-only to SPI
MC68HC708XL36
SPI Status
I/O Signals
227
SPI