M66596FP datasheet(39/131 Pages) RENESAS

39 / 131 page

M66596FP/WG

rev .1.00

2006.3.14

page 39 of 127

2.10.1 Isochronous errors

With this controller, data transfer errors that occur in isochronous transfers can be confirmed using the OVRN

bit and the CRCE bit of the FRMNUM register. In isochronous transfers, error notification by the NRDY

interrupt can be differentiated using the OVRN bit and the CRCE bit between data buffer errors and packet

errors.

Table 2.9 and Table 2.10 show the conditions under which the OVRN bit and CRCE bit are set to “1”.

Table 2.9 Error information when an NRDY interrupt is issued in an isochronous transfer reciving direction

Bit status

Issued when:

Issue conditions

Detected error

Operation

“OVRN=1"

Data packet is

received

A new data packet is received

before reading of buffer

memory is completed

Reception data buffer

overrun

The new data packet is

thrown out

“CRCE=1"

Data packet is

received

A CRC error, or, a bit stuffing

error is detected

Received packet error

The new data is packet

thrown out

Table 2.10 Error information when an NRDY interrupt is issued in an isochronous transfer sending direction

Bit status

Issued when:

Issue conditions

Detected error

Operation

"OVRN=1"

IN token is

received

An in-token is received before

writing to buffer memory is

completed

Transmission data buffer

underrun

Zero-Length packet

transmission

"CRCE=1"

Not issued

2.10.2 SOF interrupts and frame numbers

The SOFR interrupt operation mode should be selected using the SOFRM bit of the FRMNUM register. Also,

the current frame number can be confirmed using the FRNM bit of the FRMNUM register and the UFRNM bit of

the UFRNUM register.

In the peripheral mode, with this controller, the frame numbers are refreshed at the timing at which SOF

packets are received. If the controller is unable to detect an SOF packet because the packet has been corrupted,

or for another reason, the FRNM value is retained until a new SOF packet is received. At that point, the FRNM

bit based on the SOF interpolation timer is not refreshed. Also, the UFRNM bit is incremented in response to a

uSOF packet being received.

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