Motorola M68HC08 Designer Reference Manual page 17

DRM014 — Rev 0
MOTOROLA
Freescale Semiconductor, Inc.
2. Host pulls the Clock line low.
3. Host pulls the Data line low as the start bit.
4. Host releases the Clock line.
5. Device pulls Clock line low.
6. Host sends out data.
7. Device releases the Clock line high and read Data.
8. Device reads the Clock line and aborts communication if the Clock
line is low.
9. Repeat steps 5 to 7 for Data 1 to Data 7 and the parity bit.
10. Device pulls the Clock line low.
11. Host releases the Data line.
12. Device releases the Clock line high.
13. Device reads the Data line high for stop signal and sends error if
the Data line is low.
14. Device pull the Data and the Clock lines low.
15. Device release the Clock and the Data lines.
STEP 1 4 7,8
CLOCK
2 5
DATA
3
6
START DATA0 DATA1 DATA2 DATA3 DATA4 DATA5 DATA6 DATA7 PARITY STOP ACK
Figure 1-9. Host to Device Communication
KBD_IN is the IRQ1 interrupt routine for receiving data from host. The
interrupt is configured to execute when a falling edge at the PTE4 (Data)
pin is detected.
USB and PS/2 Multimedia Keyboard Interface
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USB and PS/2 Multimedia Keyboard Interface
Firmware Description
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