MC68HC711PH8 Motorola, MC68HC711PH8 Datasheet - Page 112

• Manufacturer Part Number: MC68HC711PH8
• Description: High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit
• Manufacturer: Motorola

6
6.1
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.
6.1.1
The push field consists of a start bit, a push synchronization bit, a push data field and a push
address field. The start consists of three time slots having the dominant logical state ‘0’. The start
marks the beginning of the message frame by violation of the rule of the Manchester code. The
push synchronization bit consists of a biphase coded ‘0’. Biphase coding will be discussed later.
The push data field consists of five bits of biphase coded data. The push address consists of three
bits of biphase coded data. Data and address are written to the lower byte of the SCI data register
(S2DRL). The push data occupies the lower five bits and the push address occupies the upper
three bits of the register.
MOTOROLA
6-2
TXD pin (true data)
Push-pull function
MI BUS wire
Time slots
Bit Þelds
Push-pull sequence
The push field
Start
MOTOROLA INTERCONNECT BUS (MI BUS)
Push
sync D0 D1 D2 D3 D4 A0 A1 A2
1 0
Figure 6-1 MI BUS timing
(driven by MCU)
Push (biphase coded)
Data
Push Þeld
Message frame
Address
Start
sync
Pull
0 1
0
1
NRZ
Data
Pull (NRZ coded)
(driven by slave)
2 3 4
Pull Þeld
End of frame
5
Stop
6 7
MC68HC11PH8
TPG