Freescale Semiconductor, Inc.
Motorola Interconnect Bus (MI BUS)
Push-pull sequence
6.3 Push-pull sequence
Communication between the MCU and the slave device always utilizes
the same frame organization. First, the MCU sends serial data to the
selected device. This data field is called the ‘push field’. At the end of the
push field, the selected device automatically sends back to the MCU the
data held during the push sequence. The MCU reads the serial data sent
by the selected device. This data is called the ‘pull field’ and contains
status information followed by the end-of-frame information from the
selected device.
Time slots
Push-pull function
TXD pin (true data)
MI BUS wire
Push (biphase coded)
Pull (NRZ coded)
1 0
0 1
0 1 2 3 4 5 6 7
Stop
Start
Push
sync
Pull
sync
Bit fields
Start
D0 D1 D2 D3 D4 A0 A1 A2
NRZ
Data
Data
Address
End of frame
Push field
(driven by MCU)
Pull field
(driven by slave)
Message frame
Figure 6-1. MI BUS timing
MC68HC11P2 — Rev 1.0
Technical Data
Motorola Interconnect Bus (MI BUS)
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