2. May 9, 20012 USB On-The-Go Implementation Trade-offs Zong Liang WU TransDimension Zong Liang WU TransDimension

3. May 9, 20013 Agenda w On-The-Go device vs. Dual role device w Dual role device: top level architecture w Basic issues: system constraints w System constraints vs. Implementation choices w Compliance & interoperability w Product decision w On-The-Go device vs. Dual role device w Dual role device: top level architecture w Basic issues: system constraints w System constraints vs. Implementation choices w Compliance & interoperability w Product decision

4. May 9, 20014 On-The-Go Device Vs. Dual Role Device w Dual role device (DRD): – Supports master negotiation protocol – Acts as master or slave, after MNP – Capable of supplying at least 4mA w On-The-Go device (OTG): – Dual Role Device – Slave-only device drawing less than 4mA from Vbus w Dual role device (DRD): – Supports master negotiation protocol – Acts as master or slave, after MNP – Capable of supplying at least 4mA w On-The-Go device (OTG): – Dual Role Device – Slave-only device drawing less than 4mA from Vbus

5. May 9, 20015 Dual Role Device Top-Level Architecture HOST Function MNP Analog Transceiver Analog Transceiver Processor Interface Processor Interface Registers Top level control Registers Top level control Systemprocessor Cable Charge Pump 5V @4mA

6. May 9, 20016 Basic Issues System Constraints w Microprocessors – Wide range of performance (uP itself or the part available for DRD) – Different interfaces: often DRD is not allowed to be system bus master w System software – Latency of HW interrupt processing u Maybe critical for Isochronous applications – Different RTOS w Microprocessors – Wide range of performance (uP itself or the part available for DRD) – Different interfaces: often DRD is not allowed to be system bus master w System software – Latency of HW interrupt processing u Maybe critical for Isochronous applications – Different RTOS

7. May 9, 20017 System Constraints Vs. Implementation Choices w Performance of the master: – Throughput supported: full 12mbits/s (as good as or even better than a PC) vs. Very limited bandwidth – Endpoint types supported: all 4 types vs. A subset – Number of devices and endpoints supported: capable of supporting many devices/endpoints simultaneously vs. Only a few endpoints w Difficulties: – How to get maximum master performance with a limited uP? – How to do in embedded applications where DRD is not allowed to be system bus master ? – How to support Isochronous applications within a RTOS having a large interrupt latency (like wince)? w Performance of the master: – Throughput supported: full 12mbits/s (as good as or even better than a PC) vs. Very limited bandwidth – Endpoint types supported: all 4 types vs. A subset – Number of devices and endpoints supported: capable of supporting many devices/endpoints simultaneously vs. Only a few endpoints w Difficulties: – How to get maximum master performance with a limited uP? – How to do in embedded applications where DRD is not allowed to be system bus master ? – How to support Isochronous applications within a RTOS having a large interrupt latency (like wince)?

8. May 9, 20018 System Constraints Vs. Implementation Choices w uP requirements vs. Master performance: – Desired target for portable or STB applications: 1. Optimal performance 2. Light load on uP 3. Minimum interrupt frequency 4. Loose requirement on uP’s interrupt latency 5. Keep at low cost (HW+SW) – Trade-off vs. Smart SW/HW partitioning Learn from OHCI and UHCI partitioning Ô Call for major architecture innovation w uP requirements vs. Master performance: – Desired target for portable or STB applications: 1. Optimal performance 2. Light load on uP 3. Minimum interrupt frequency 4. Loose requirement on uP’s interrupt latency 5. Keep at low cost (HW+SW) – Trade-off vs. Smart SW/HW partitioning Learn from OHCI and UHCI partitioning Ô Call for major architecture innovation

9. May 9, 20019 System Constraints Vs. Implementation Choices w Many applications: – Portable ( PDA, mobile phone, MP3, pocket PC, digital camera etc ) and less portable ( set-top-box, game machine, etc ): Ô Many RTOS on the market w RTOS-based stack vs. Dedicated system SW – RTOS is not always necessary – Think of a dedicated microprocessor w RTOS-based: how to design once for all? – Try to comply with and reuse OHCI/UHCI stack – Partner with specialty system software house w Many applications: – Portable ( PDA, mobile phone, MP3, pocket PC, digital camera etc ) and less portable ( set-top-box, game machine, etc ): Ô Many RTOS on the market w RTOS-based stack vs. Dedicated system SW – RTOS is not always necessary – Think of a dedicated microprocessor w RTOS-based: how to design once for all? – Try to comply with and reuse OHCI/UHCI stack – Partner with specialty system software house

10. May 9, 200110 System Constraints Vs. Implementation Choices w Power management: – Portable appliances require low power – OTG spec introduces the concept of session and wakeup protocol – Manage power at chip architecture level, by introducing appropriate power management logic w Power management: – Portable appliances require low power – OTG spec introduces the concept of session and wakeup protocol – Manage power at chip architecture level, by introducing appropriate power management logic

11. May 9, 200111 System Constraints Vs. Implementation Choices w Single chip vs. 2-chip solution – OTG master needs to supply 5V@4mA (minimum) – Analog transceiver’s signaling is 3.3V – Standard 0.18um process has trouble to implement u Put the charge pump and the analog transceiver into a separate chip u Define a standard interface: ongoing effort w Single chip vs. 2-chip solution – OTG master needs to supply 5V@4mA (minimum) – Analog transceiver’s signaling is 3.3V – Standard 0.18um process has trouble to implement u Put the charge pump and the analog transceiver into a separate chip u Define a standard interface: ongoing effort

12. May 9, 200112 Compliance & Interoperability w Compliance to WHAT: – A DRD must be a 100% compliant USB function – OTG master vs. Embedded master vs. Standard PC host (OHCI/UHCI): u OTG: one to one: simpler master u Embedded: Strong sales point if the master can support what a standard PC host can do (endpoint types, number, sizes) w An OTG compliance spec is in development w Compliance to WHAT: – A DRD must be a 100% compliant USB function – OTG master vs. Embedded master vs. Standard PC host (OHCI/UHCI): u OTG: one to one: simpler master u Embedded: Strong sales point if the master can support what a standard PC host can do (endpoint types, number, sizes) w An OTG compliance spec is in development

13. May 9, 200113 Product Decision w What do you really want: 1.Slave-only with mini-connector and draws <=4ma 2.Dual role device (master or slave depending on MNP result) 3.Simultaneous master and slave w Do not forget your expectation on master’s performance w Discrete IC or integrate an IP into your system: – Time to market vs. Cost vs. Risk w What do you really want: 1.Slave-only with mini-connector and draws <=4ma 2.Dual role device (master or slave depending on MNP result) 3.Simultaneous master and slave w Do not forget your expectation on master’s performance w Discrete IC or integrate an IP into your system: – Time to market vs. Cost vs. Risk