SH7751 Group, SH7751R Group
Section 14 Direct Memory Access Controller (DMAC)
R01UH0457EJ0301 Rev. 3.01
Page 555 of 1128
Sep 24, 2013
14.5.2
Pins in DDT Mode
Figure 14.24 shows the system configuration in DDT mode.
Synchronous
DRAM
DBREQ
/
DREQ0
BAVL
/DRAK0
TR
/
DREQ1
TDACK
/DACK0
ID1, ID0/DRAK1, DACK1
CKIO
D31–D0 = DTR
External device
SH7751/SH7751R
A25–A0, RAS, CAS, WE, DQMn, CKE
Figure 14.24 System Configuration in On-Demand Data Transfer Mode
•
DBREQ
:
Data bus release request signal for transmitting the data transfer request format (DTR
format) or a DMA request from an external device to the DMAC
If there is a wait for release of the data bus, an external device can have the data bus released
by asserting
DBREQ
. When
DBREQ
is accepted, the BSC asserts
BAVL
.
•
BAVL
:
Data bus D31–D0 release signal
Assertion of
BAVL
means that the data bus will be released two cycles later.
•
TR
:
Transfer request signal
Assertion of
TR
has the following different meanings.
⎯
In normal data transfer mode (channel 0, except channel 0),
TR
is asserted, and at the same
time the DTR format is output, two cycles after
BAVL
is asserted.
⎯
In the case of the handshake protocol without use of the data bus, asserting
TR
enables a
transfer request to be issued for the channel for which a transfer request was made
immediately before. This function can be used only when
BAVL
is not asserted two cycles
earlier.
⎯
In the case of direct data transfer mode (valid only for channel 2), a direct transfer request
can be made to channel 2 by asserting
DBREQ
and
TR
simultaneously.