DATA TRANSFER CONTROL DEVICE AND DATA TRANSFER CONTROL METHOD
A data transfer control device in accordance with an exemplary aspect of the present invention includes a first communication unit that processes data transfer with a peripheral device, and a second communication unit that processes data transfer with a host device, wherein one of the first and second communication units serves as a preferential communication unit whose data transfer should have a high priority, and another of the first and second communication units serves as a non-preferential communication unit, when the data transfer is being performed in the preferential communication unit, the preferential communication unit notifies the non-preferential communication unit that the data transfer is being performed, and when the non-preferential communication unit is being notified that the data transfer is being performed from the preferential communication unit, the non-preferential communication unit puts the data transfer in the non-preferential communication unit on hold.
1 . A data transfer control device comprising:
a first communication unit that processes data transfer with a peripheral device; and
a second communication unit that processes data transfer with a host device, wherein
one of the first and second communication units serves as a preferential communication unit whose data transfer should have a high priority, and another of the first and second communication units serves as a non-preferential communication unit,
when the data transfer is being performed in the preferential communication unit, the preferential communication unit notifies the non-preferential communication unit that the data transfer is being performed, and
when the non-preferential communication unit is being notified that the data transfer is being performed from the preferential communication unit, the non-preferential communication unit puts the data transfer in the non-preferential communication unit on hold.
2 . The data transfer control device according to claim 1 , further comprising a register that stores communication unit designation information designating either the first communication unit or the second communication unit as the preferential communication unit,
wherein when the data transfer is started, the first communication unit and the second communication unit notify whether the data transfer is being performed or not according to the communication unit designation information stored in the register.
3 . The data transfer control device according to claim 1 , wherein
the first communication unit itself is the preferential communication unit; and when data transfer is started between the first communication unit itself and the peripheral device, the first communication unit notifies the second communication unit that data transfer with the peripheral device is being performed, and
when second communication unit is being notified that the first communication unit is performing data transfer with the peripheral device from the first communication unit, the second communication unit transmits a transfer disabled response indicating that data transfer to the host device cannot be performed in response to a data transfer start request from the host device.
4 . The data transfer control device according to claim 3 , wherein when data transfer between the peripheral device and the first communication unit is started during data transfer between the second communication unit and the host device, the second communication unit transmits the transfer disabled response in response to the data transfer start request that is sent from the host device when or after current data transfer is completed.
5 . The data transfer control device according to claim 3 , wherein
the first communication unit outputs a transfer permission/denial signal used to notify permission/denial of data transfer between the second communication unit and the host device to the second communication unit, and
the second communication unit enters a data transfer disabled mode, in which the transfer disabled response is transmitted in response to a data transfer start request from the host device, according to the transfer permission/denial signal.
6 . The data transfer control device according to claim 1 , wherein
the second communication unit itself is the preferential communication unit; and when data transfer is started between the second communication unit itself and the host device, the second communication unit notifies the first communication unit that data transfer with the host device is being performed, and
when the first communication unit is being notified that the second communication unit is performing data transfer with the host device from the second communication unit, the first communication unit puts transmission of a data transfer start request to the peripheral device on hold; and when the first communication unit is being notified that the second communication unit has completed the data transfer with the host device, the first communication unit transmits the data transfer start request that was put on hold to the peripheral device.
7 . The data transfer control device according to claim 6 , wherein when data transfer between the host device and the second communication unit is started during data transfer between the first communication unit and the peripheral device, the first communication unit puts transmission of the data transfer start request to the peripheral device that is to be performed when or after current data transfer is completed on hold.
8 . The data transfer control device according to claim 6 , wherein
the second communication unit outputs a transfer hold request signal to the first communication unit, the transfer hold request signal being used to notify a request for putting data transfer between the first communication unit and the peripheral device on hold, and
the first communication unit enters a data transfer hold mode, in which a data transfer start request to the peripheral device is put on hold, according to the transfer hold request signal.
9 . The data transfer control device according to claim 5 , wherein
the first communication unit comprises a plurality of transfer execution units each of which performs data transfer with a respective one of a plurality of endpoints of the peripheral device,
the first communication unit transmits the transfer permission/denial signal set to an active state to the second communication unit from when data transfer with the peripheral device is started in one of the plurality of transfer execution units to when the data transfer is finished in all transfer execution units that have been performing data transfer with the peripheral device, and
the second communication unit enters the data transfer disabled mode when the transfer permission/denial signal is an active state.
10 . The data transfer control device according to claim 9 , each of the plurality of transfer execution units comprises a notification determination unit that determines whether or not a situation where data transfer is being performed with the peripheral device should be notified to the second communication unit,
the first communication unit transmits the transfer permission/denial signal set to an active state to the second communication unit when there is a transfer execution unit, among transfer execution units that are performing data transfer with the peripheral device, that is determined to be notified to the second communication unit by the notification determination unit, and
the second communication unit enters the data transfer disabled mode when the transfer permission/denial signal is an active state.
11 . The data transfer control device according to claim 9 ,
when transmission to the second communication unit for which the transfer permission/denial signal is brought to an active state has continued for a predetermined time or longer, the first communication unit sets the transfer permission/denial signal to an inactive state and transmits the inactive transfer permission/denial signal to the second communication unit, and
the second communication unit enters a mode other than the data transfer disabled mode when the transfer permission/denial signal is an inactive state.
12 . The data transfer control device according to claim 3 ,
data transfer between the peripheral device and the first communication unit and data transfer between the host device and the second communication unit are transfer based on USB (Universal Serial Bus) standards, and
when the second communication unit receives an IN, OUT, or PING token from the host device in bulk transfer or interrupt transfer, the second communication unit sends back a NAK (Negative AcKnowledgement) response.
13 . The data transfer control device according to claim 1 , further comprising a state management register that holds a data transfer state between the peripheral device and the first communication unit,
wherein when data transfer is started between the peripheral device and the first communication unit, the second communication unit stores information indicating that data transfer is being performed in the state management register; and when the data transfer is completed, the second communication unit clears the information stored in the state management register.
14 . The data transfer control device according to claim 8 , wherein
the second communication unit comprises a plurality of endpoints each of which performs data transfer with a respective one of a plurality of transfer execution units of the host device,
the second communication unit transmits the transfer hold request signal set to an active state to the first communication unit from when data transfer with the host device is started in one of the plurality of endpoints to when the data transfer is finished in all endpoints that have been performing data transfer with the host device, and
the first communication unit enters the data transfer hold mode when the transfer hold request signal is an active state.
15 . The data transfer control device according to claim 14 , each of the plurality of endpoints comprises a notification determination unit that determines whether or not a situation where data transfer is being performed with the host device should be notified to the first communication unit,
the second communication unit transmits the transfer hold request signal set to an active state to the first communication unit when there is an endpoint, among endpoints that are performing data transfer with the host device, that is determined to be notified to the first communication unit by the notification determination unit, and
the first communication unit enters the data transfer hold mode when the transfer hold request signal is an active state.
16 . A data transfer control method to control a data transfer control device comprising a first communication unit that processes data transfer with a peripheral device, and a second communication unit that processes data transfer with a host device, wherein
one of the first and second communication units serves as a preferential communication unit whose data transfer should have a high priority, and another of the first and second communication units serves as a non-preferential communication unit,
when the data transfer is being performed in the preferential communication unit, the preferential communication unit notifies the non-preferential communication unit that the data transfer is being performed, and
when the non-preferential communication unit is being notified that the data transfer is being performed from the preferential communication unit, the non-preferential communication unit puts the data transfer in the non-preferential communication unit on hold.
17 . The data transfer control method according to claim 16 ,
wherein the data transfer control device further comprises a register that stores communication unit designation information designating either the first communication unit or the second communication unit as the preferential communication unit,
the data transfer control device externally accepts communication unit designation information designating either the first communication unit or the second communication unit as a communication unit whose data transfer should have a higher priority, and stores the accepted communication unit designation information in a register,
when data transfer between the first communication unit and the peripheral device is started, the first communication unit notifies the second communication unit of whether or not the first communication unit is performing data transfer with the peripheral device according to the communication unit designation information stored in the register, and
when data transfer between the second communication unit and the host device is started, the second communication unit notifies the first communication unit of whether or not the second communication unit is performing data transfer with the host device according to the communication unit designation information stored in the register.
18 . The data transfer control method according to claim 16 , wherein
the first communication unit itself is the preferential communication unit; and when data transfer is started between the first communication unit itself and the peripheral device, the first communication unit notifies the second communication unit that the first communication unit is performing data transfer with the peripheral device,
when second communication unit is being notified that the first communication unit is performing data transfer with the peripheral device from the first communication unit, the second communication unit transmits a transfer disabled response indicating that data transfer to the host device cannot be performed in response to a data transfer start request from the host device,
the first communication unit itself is the preferential communication unit; and when data transfer between the first communication unit itself and the peripheral device is completed, the first communication unit notifies the second communication unit that the first communication unit has completed the data transfer with the peripheral device, and
when second communication unit is being notified that the first communication unit has completed the data transfer with the peripheral device from the first communication unit, the second communication unit transmits a response in response to a data transfer start request from the host device, the response being used to start data transfer with the host device.
19 . The data transfer control method according to claim 16 , wherein
the second communication unit itself is the preferential communication unit; and when data transfer is started between the second communication unit itself and the host device, the second communication unit notifies the first communication unit that the second communication unit is performing data transfer with the host device,
when first communication unit is being notified that the second communication unit is performing data transfer with the host device from the second communication unit, the first communication unit puts transmission of a data transfer start request to the peripheral device on hold,
the second communication unit itself is the preferential communication unit; and when data transfer between the second communication unit itself and the host device is completed, the second communication unit notifies the first communication unit that the second communication unit has completed the data transfer with the host device, and
when first communication unit is being notified that the second communication unit has completed the data transfer with the host device from the second communication unit, the first communication unit transmits the data transfer start request that was put on hold to the peripheral device.
20 . The data transfer control method according to claim 17 , wherein
the first communication unit outputs a transfer permission/denial signal used to notify permission/denial of data transfer between the second communication unit and the host device to the second communication unit according to the communication unit designation information,
the second communication unit enters a data transfer disabled mode, in which the transfer disabled response is transmitted in response to a data transfer start request from the host device, according to the transfer permission/denial signal,
the second communication unit outputs a transfer hold request signal to the first communication unit according to the communication unit designation information, the transfer hold request signal being used to notify a request for putting data transfer between the first communication unit and the peripheral device on hold, and
the first communication unit enters a data transfer hold mode, in which a data transfer start request to the peripheral device is put on hold, according to the transfer hold request signal.