mc68hc708mp16 Freescale Semiconductor, Inc, mc68hc708mp16 Datasheet - Page 275

• Manufacturer Part Number: mc68hc708mp16
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

MC68HC708MP16
Freescale Semiconductor
NOTE:
—
Rev. 3.1
When an SPI is configured as a slave, the SS pin is always configured
as an input. It cannot be used as a general purpose I/O regardless of the
state of the MODFEN control bit. However, the MODFEN bit can still
prevent the state of the SS from creating a MODF error. (See
SPI Status and Control
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
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
MASTER SS
MISO/MOSI
(CPHA = 0)
(CPHA = 1)
SLAVE SS
SLAVE SS
13-3.)
Serial Peripheral Interface Module (SPI)
Figure 13-12. CPHA/SS Timing
BYTE 1
13.8.2 Mode Fault
Register.)
BYTE 2
Serial Peripheral Interface Module (SPI)
Error.) For the state of the
BYTE 3
Technical Data
13.14.2
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