mc68hc705v12 Freescale Semiconductor, Inc, mc68hc705v12 Datasheet - Page 111

• Manufacturer Part Number: mc68hc705v12
• Description: M68hc05-based Mcu Hc05 Freescale Semiconductor
• Manufacturer: Freescale Semiconductor, Inc

10.7 SPI in Stop Mode
10.8 SPI in Wait Mode
MC68HC705V12
—
Rev. 3.0
When the MCU enters stop mode, the baud rate generator driving the
SPI shuts down. This essentially stops all master mode SPI operation;
thus, the master SPI is unable to transmit or receive any data. If the
STOP instruction is executed during an SPI transfer, that transfer is
halted until the MCU exits stop mode (provided it is an exit resulting from
a viable interrupt source). If the stop mode is exited by a reset, then the
appropriate control/status bits are cleared and the SPI is disabled. If the
device is in slave mode when the STOP instruction is executed, the
slave SPI will still operate. It can still accept data and clock information
in addition to transmitting its own data back to a master device.
At the end of a possible transmission with a slave SPI in stop mode, no
flags are set until a viable interrupt results in an MCU wake up. Be
cautious when operating the SPI (as a slave) during stop mode because
none of the protection circuitry (write collision, mode fault, etc.) is active.
Also note that when the MCU enters stop mode, all enabled output
drivers (MISO, MOSI, and SCLK ports) remain active and any sourcing
currents from these outputs will be part of the total supply current
required by the device.
The SPI subsystem remains active in wait mode. Therefore, it is
consuming power. Before reducing power, the SPI should be shut off
prior to entering wait mode. A non-reset exit from wait mode will result in
the state of the SPI being unchanged. A reset exit will return the SPI to
its reset state, which is disabled.
Freescale Semiconductor, Inc.
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Serial Peripheral Interface (SPI)
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Serial Peripheral Interface (SPI)
Advance Information
SPI in Stop Mode