Hitachi SH7095 Hardware User Manual page 259

Table 9.8 Relationship of Request Modes and Bus Modes by DMA Transfer Category
Address
Mode Transfer Category
Single External device with DACK and external memory
External device with DACK and memory-mapped
external device
Dual External memory and external memory
External memory and memory-mapped external
device
Memory-mapped external device and memory-
mapped external device
External memory and on-chip peripheral module
Memory-mapped external device and on-chip
peripheral module
On-chip peripheral module and on-chip peripheral
module
B: Burst, C: Cycle-steal
Notes: 1. External requests and auto requests are both available. SCI cannot be specified as the
transfer request source, however, except for on-chip peripheral module requests.
2. External requests, auto requests and on-chip peripheral module requests are all
available. When the SCI is the transfer request source, however, the transfer
destination or transfer source must both be the SCI.
3. If the transfer request source is the SCI, cycle-steal (C) only (DREQ by edge, low
active).
4. The access size is that permitted by the register of the on-chip peripheral module that is
the transfer destination or source.
Bus Mode and Channel Priority: When a given channel (1) is transferring in burst mode and
there is a transfer request to a channel (0) with a higher priority, the transfer of the channel with
higher priority (0) will begin immediately. When channel 0 is also operating in the burst mode, the
channel 1 transfer will continue as soon as the channel 0 transfer has completely finished. When
channel 0 is in the cycle-steal mode, channel 1 will begin operating again after channel 0
completes the transfer of one transfer unit, but the bus will then switch between the two in the
order channel 1, channel 0, channel 1, channel 0. Since channel 1 is in burst mode, it will not give
the bus to the CPU. This example is illustrated in Figure 9.12.
248 Hitachi
Request Bus
Mode Mode
External B/C
External B/C
*1
All B/C
*1
All B/C
*1
All B/C
*2 *3
All B/C
*2 *3
All B/C
*2 *3
All B/C
Transfer
Size
(Bytes)
1/2/4
1/2/4
1/2/4/16
1/2/4/16
1/2/4/16
*4
1/2/4/16
*4
1/2/4/16
*4
1/2/4/16