HD6417641 RENESAS [Renesas Technology Corp], HD6417641 Datasheet - Page 477

• Manufacturer Part Number: HD6417641
• Manufacturer: RENESAS [Renesas Technology Corp]

Table 13.5 Selecting External Request Detection with Dl, DS Bits
When DREQ is accepted, the DREQ pin becomes request accept disabled state (non-sensitive
period). After issuing acknowledge signal DACK for the accepted DREQ, the DREQ pin again
becomes request accept enabled state.
When DREQ is used by level detection, there are following two cases by the timing to detect the
next DREQ after outputting DACK.
Overrun0: Transfer is aborted after the same number of transfer has been performed as requests.
Overrun1: Transfer is aborted after transfers have been performed for (the number of requests
plus 1) times.
The DO bit in CHCR selects this overrun 0 or overrun 1.
Table 13.6 Selecting External Request Detection with DO Bit
DL
0
1
CHCR_0 or CHCR_1
DO
0
1
CHCR
DS
0
1
0
1
Detection of External Request
Low level detection
Falling edge detection
High level detection
Rising edge detection
External Request
Overrun 0
Overrun 1
Section 13 Direct Memory Access Controller (DMAC)
Rev. 4.00 Sep. 14, 2005 Page 427 of 982
REJ09B0023-0400