Button Status And Z Displacement Packet; Packet Format For Button And Z Displacement; Start Field; Button Status Byte - Motorola M68HC08 Designer Reference Manual

Mouse Transmitter Firmware

5.3.3 Button Status and Z Displacement Packet

DRM055
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Freescale Semiconductor, Inc.
Figure 5-4 shows the packet format for button and Z displacement.
Start Button Status

START FIELD

Figure 5-4. Packet Format for Button and Z Displacement
The start field consists of the SYNC pattern, preamble, and a header as shown
in Figure 5-5.
SYNC PATTERN AND PREAMBLE
The button status byte (Figure
shows which buttons are pressed or released. The bit value of '1' means the
button was pressed and '0' means the button was released
R ID M-BTN R-BTN L-BTN
Figure 5-6. Button Status Byte
This byte represents either the Z displacement or the new ID code
The Z displacement byte represents the Z displacement in 2's complement if
the ID bit in the button status equals '0'. If the ID bit equals '1', it represents the
new ID code.
Bit 7 Bit 6 Bit 5
Figure 5-7. Z Displacement or ID Byte
The checksum is the sum of the button status byte, the Z Displacement byte,
and the stored ID byte. See
Bit 7 Bit 6 Bit 5
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Z or ID
DATA FIELD
(12T PERIOD)
Figure 5-5. Start Field
5-6) represents the status of the four buttons. It
R
Bit 4 Bit 3 Bit 2
Figure 5-8.
Bit 4 Bit 3 Bit 2
Figure 5-8. Checksum Byte
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Checksum
CHECKSUM FIELD
HEADER
(6T PERIOD)
R R STOP
(Figure 5-7).
Bit 1 Bit 0 STOP
Bit 1 Bit 0 STOP
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