HD64570 Datasheet, PDF (42/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

1.7.9 DMAC
The DMAC module in the SCA has four independent channels (figure 1.14). The DMAC is used
exclusively for single-address transfer between memory and the MSCI. Data can be transferred a
word at a time or a byte at a time. A group of data transferred consecutively is referred to as a
block. The DMAC can transfer single blocks individually, or can transfer a chained sequence of
blocks (chained-block transfer). See figure 1.15 to 1.20.
Features:
• Four independent DMA channels
• Programmable channel priority
• Used exclusively for transfer between memory and MSCI
• Single-block transfer or chained-block transfer (supported by buffer management function)
• Two interrupt sources
• Maximum transfer rate: 11.1 Mbytes/s (operating on 16.7 MHz clock)
• Address space: 16 Mbytes
Data
bus
DMAC
Channel 0
Channel 1
Channel 2
Channel 3
MSCI
Channel 0
receiver
Channel 0
transmitter
Channel 1
receiver
Channel 1
transmitter
Receive data
Transmit data
Receive data
Transmit data
Figure 1.14 Interconnections between DMA Channels and MSCI Channels (concept)
Rev. 0, 07/98, page 26 of 453