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Section 21 IEBus
TM
Controller
R01UH0134EJ0400 Rev. 4.00 Page 1149 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
21.8 Usage Notes
21.8.1 Note on Operation when Transfer is Incomplete after Transfer of the Maximum
Number of Bytes
(1) Data Transmission
When the maximum number of bytes defined by the communications mode have been transmitted
because a NAK has been received from the receive unit or transmission has not been completed
because the message length value exceeds the maximum number of transfer bytes in one frame,
this module sets the error flag and enters a wait state. At this time, transfer proceeds until the (n +
1)th byte has been transmitted, where n is the maximum number of transfer bytes. Then, when
NAK is received via the acknowledge bit of the (n + 1)th byte, the TXERO flag is set. If ACK is
received rather than NAK, the TXF flag is set.
Figure 21.18 shows the timing of operations when the maximum number of transfer bytes is
reached but transmission has not been completed.
[Legend]
HD: Header
MA: Master address field
SA: Slave address field
CT: Control field
DL: Message length field
Dn: Data field (n = Maximum number of transfer bytes)
Master
transmission
IETSR
TXERO
TXF
Dn+1Dn-1 Dn
HD
MA SA CT
DL
D1 D2
When ACK is received for Dn + 1
When NAK is received for Dn + 1
Figure 21.18 Timing of Operations when Transmission Has Not Been Completed
Within the Maximum Number of Transfer Bytes