As the HT82A851R is a USB device how can the device send a 0-sized data packet to the main controller?
Answer When the microcontroller sends a 0-sized data packet to the main controller, this is in effect just sending a handshake signal to the main controller. The method of transmission is as follows: 1. Set bit 1, which is the TX bit, of the MISC register to 1 to put the FIFO into the write mode. 2. Delay 4us. 3. Set bit 0, which is the REQUEST bit, of the MISC register to 1, this will send a FIFO request. 4. Delay 28us 5. Determine if bit 6, which is the READY bit, of the MISC register is equal to 1. If not equal to 1 then proceed to step 1, if equal to 1 then proceed to step 6. 6. Clear bit 1, the TX bit, of the MISC register to 0. This will place the FIFO into the read mode. 7. Delay 4us 8. Clear bit 0, the REQUEST bit, of the MISC register to 0. This will end the FIFO request. When the above operation has completed, then the microcontroller has just sent a 0-sized data packet to the main controller.
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