
I/O Model Reference 111
Up to 255 bytes can be bi-directionally transferred at a time. This I/O model
depends on interrupts to process data at high speed and does not use the io_in()
and io_out() function calls. After transfer is initiated, control is returned to the
application immediately, and the application needs to poll the I/O model for
completion. Transfers can be suspended and resumed by disabling and enabling
interrupts. Turning off interrupts might be required when going off-line, or for
assuring that other time-critical application execution is not disturbed by
background interrupts. Additionally, transfers can be aborted.
[default] (CPOL = 1)
Present bit
Sample bit
Invert (CPOL = 0)
SS
MISO
MOSI
msb lsbbit5 bit4bit6 bit2bit3 bit1
msb lsbbit5 bit4bit6 bit2bit3 bit1
Figure 39. Transmission Timing for Clockedge(-) (CPHA : 0)
[default] (CPOL = 1)
Present bit
Sample bit
invert (CPOL = 0)
SS
MISO
MOSI
msb lsbbit5 bit4bit6 bit2bit3 bit1
msb lsbbit5 bit4bit6 bit2bit3 bit1
Figure 40. Transmission Timing for Clockedge(+) (CPHA : 1)
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