Datasheet

254
7593L–AVR–09/12
AT90USB64/128
22.9 OTG timers customizing
It is possible to refine some OTG timers thanks to the OTGTCON register that contains the
PAGE bits to select the timer and the VALUE bits to adjust the value. User should refer to lastest
releases of the OTG specification to select compliant timings.
• PAGE=00b: AWaitVrise time-out. [OTG]. In Host mode, once VBUSREQ has been set to “1”,
if no VBUS is detected on VBUS pin after this AWaitVrise delay then the VBERRI error flag is
set.
– VALUE=00bTime-out is set to 20ms
– VALUE=01bTime-out is set to 50ms
– VALUE=10bTime-out is set to 70ms
– VALUE=11bTime-out is set to 100ms
• PAGE=01b: VbBusPulsing. [OTG]. In Device mode, this delay corresponds to the pulse
duration on Vbus during a SRP.
– VALUE=00bTime-out is set to 15ms
– VALUE=01bTime-out is set to 23ms
– VALUE=10bTime-out is set to 31ms
– VALUE=11bTime-out is set to 40ms
• PAGE=10b: PdTmOutCnt. [OTG]. In Device mode, when a SRP has been requested to be
sent by the firmware, this delay is waited by the hardware after VBUS has gone below the
“session_valid” threshold voltage and before initiating the first pulse. This delay should be
considered as an approximation of USB lines discharge (pull-down resistors vs. line
capacitance) in order to wait that VBUS has gone below the “b_session_end” threshold
voltae, as defined in the OTG specification.
– VALUE=00bTime-out is set to 93ms
– VALUE=01bTime-out is set to 105ms
– VALUE=10bTime-out is set to 118ms
– VALUE=11bTime-out is set to 131ms
• PAGE=11b: SRPDetTmOut. [OTG]. In Host mode, this delay is the minimum pulse duration
required to detect and accept a valid SRP from a Device.
– VALUE=00bTime-out is set to 1µs
– VALUE=01bTime-out is set to 100µs
– VALUE=10bTime-out is set to 1ms
– VALUE=11bTime-out is set to 11ms