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IDMA Channels
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MC68360 USER’S MANUAL
Up to 50 Mbyte/sec Transfer Rates in Single Address Mode and 25 Mbyte/sec in Dual
Address Mode (assuming a 25-MHz system clock)
32-Bit Byte Transfer Counters
32-Bit Address Pointers That Can Increment or Remain Constant
Operand Packing and Unpacking for Dual Address Transfers using the Most Efficient
Techniques
Supports All Bus-Termination Modes
Provides Full DMA Handshake for Cycle Steal and Burst Transfers
Supports Fixed and Rotating Priority Between IDMA Channels
Buffer Handling Modes: Single Buffer, Auto Buffer, and Buffer Chaining
7.6.2 IDMA Registers
Each IDMA channel has eight registers that define its specific operation. These registers
include a 32-bit source address pointer register (SAPR), a 32-bit destination address pointer
register (DAPR), an 8-bit function code register (FCR), a 32-bit byte count register (BCR), a
16-bit channel mode register (CMR), an 16-bit channel configuration register (ICCR), an 8-
bit channel status register (CSR), and an 8-bit channel mask register (CMAR). These regis-
ters provide the addresses, transfer count, and configuration information necessary to set
up a transfer. They also provide a means of controlling the IDMA channel and monitoring its
status. All registers can be modified by the CPU32+ core.
For the auto buffer and buffer chaining modes, the RISC controller uses a buffer descriptor
ring to automatically initialize the DAPR, SAPR, and BCR. The buffer descriptor ring resides
in dual-port RAM so that it may be accessed by the RISC controller without bus overhead.
The IDMA channel also includes a 32-bit data holding register (DHR), which is not accessi-
ble to the CPU32+ core and is used by the IDMA for temporary data storage.
7.6.2.1 IDMA CHANNEL CONFIGURATION REGISTER (ICCR). The 16-bit ICCR config-
ures both IDMA channels. It is always readable and writable in the supervisor mode,
although writing is not recommended unless the module is disabled. It is initialized to $0000
at reset.
STP—Stop Bit
0 = The system clock operates normally within the IDMA.
1 = Stop the system clock to the IDMA channels. This setting is used to conserve pow-
er when both IDMAs are unused.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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