Fujitsu MB96300 series Hardware Manual page 811

30.5.6 Retry Function
This function enables the transfer error handling by retry.
■ Retry Function
The retry function is enabled (i.e. HCNT1:RETRY is set to "1"), when NAK or an error such as
CRC error occurs, the function will continue to retry the transfer during a time period set in the
retry timer register (HRTIMER).
If an error except STALL and disconnected device happens, it retries to process the token as
long as the HCNT1:RETRY bit is set and the retry time out has not elapsed.
The retry can be stopped by the following conditions:
• Detecting 0 in the retry timer
• The occurrence of an interrupt due to SOF (HCNT0:SOFIRE = "1" and HIRQ:SOFIRQ = "1")
• ACK Detection
• Device disconnection detection
The retry timer is activated when the token processing starts, decrements the register value, and
stops counting when a retry happens in an EOF area. If HIRQ:SOFIRQ bit is "0", the retry timer
restarts from the last value hold in the counter when it stopped. When the SOF token is complete
or when the timer reaches "0" or a packet ends, any retry request it receives is cancelled and the
packet will be terminated.
Token beginning
When the retry operation is completed, end information on the complete packet is set in related
registers.
Figure 30.5-5 Retry Timer Operation (HIRQ:SOFIRQ = "0")
Token execution
Timer countdown
EOF SOF
Timer stop
Retry generation
CHAPTER 30 USB Mini-host
retry
Timer restart
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