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Advanced Technology Attachment (ATA)
23-2
Freescale Semiconductor
•
One CPU bus for communication with the host processor
•
One DMA bus for communication with the host DMA unit
All internal registers are visible from both busses, allowing smart DMA access to program the interface.
Before accessing the ATA bus, the host must program the timing parameters on the ATA bus. The timing
parameters control the timing on the ATA bus. Most timing parameters are programmable as a number of
clock cycles (1 to 255). Some are implied.
After programming the timing parameters, two protocols can be active at the same time on the ATA bus:
PIO or DMA mode. All transfers between the FIFO and host or DMA busses are zero wait states transfer,
so high speed transfer between FIFO and DMA/host bus is possible.
When a PIO access performed during a running DMA transfer, the DMA transfer pauses, the PIO access
finishes, and the DMA transfer resumes again.
NOTE
The pin multiplexing and control module must be configured to enable the
peripheral function of the appropriate pins (refer to
) prior to configuring the ATA.
23.1.2
Features
The ATA interface has these features:
•
Programmable timing on the ATA bus. Works with wide range of bus frequencies.
•
Compliant with
AT Attachment - 6 with Packet Interface
specification found at
— Supports programmed input/output (PIO) modes 0, 1, 2, 3, and 4
— Supports multiword DMA modes 0, 1, and 2
— Supports ultra DMA modes 0, 1, 2, 3, 4, and 5
•
128-byte FIFO interface
•
FIFO receive alarm, FIFO transmit alarm, and FIFO end of transmission alarm to DMA unit
•
Zero-wait cycles transfer between DMA bus and FIFO allows fast FIFO reading/writing
23.1.3
Modes of Operation
The interface offers two operating modes:
•
PIO Mode
An access to the ATA bus in PIO mode occurs when the host CPU or the host DMA unit reads or
writes ATA PIO register. During PIO transfer the incoming device bus cycle translates to an ATA
PIO bus cycle by the ATA protocol engine. No buffering of data occurs, so the host CPU or host
DMA cycle stalls until the ATA bus read data is available on read or stalls until the device bus data
can be put on the ATA bus during write.
PIO accesses can happen to the bus at any time, even during a running ATA DMA transfer. In this
case, the DMA transfer pauses, the PIO cycle completes, and the DMA transfer resumes.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...