Freescale Semiconductor, Inc.
Sim p le Se ria l Inte rfa c e
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
SDO
(IDLE = 0)
SCK
(CPHA = 1)
100 ns
100 ns
SDI
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
Figure 9-3. SIOP Timing Diagram (CPHA = 1)
9.3.2 Se ria l Da ta Inp ut (SDI)
The SDI pin becomes an input as soon as the SIOP subsystem is
enabled. New data is presented to the SDI pin on the falling edge of
SCK. Valid data must be present at least 100 nanoseconds before the
rising edge of SCK and remain valid for 100 nanoseconds after the rising
edge of SCK. See Figure 9-3.
9.3.3 Se ria l Da ta Outp ut (SDO)
The SDO pin becomes an output as soon as the SIOP subsystem is
enabled. The state of the PB5/SDO pin reflects the value of the first bit
received on the previous transmission. Prior to enabling the SIOP, the
PB5/SDO can be initialized to determine the beginning state. While
SIOP is enabled, the port B logic cannot be used as a standard output
since that pin is connected to the last stage of the SIOP serial shift
register. A control bit (LSBF) is included in the SCR to allow the data to
be transmitted in either the MSB first format or the LSB first format.
The first data bit will be shifted out to the SDO pin on the first falling edge
of the SCK. The remaining data bits will be shifted out to the SDI pin on
subsequent falling edges of SCK. The SDO pin will present valid data at
least 100 nanoseconds before the rising edge of the SCK and remain
valid for 100 nanoseconds after the rising edge of SCK. See Figure 9-3.
General Release Specification
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
Simple Serial Interface
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