![Freescale Semiconductor MCF54455 Reference Manual Download Page 578](http://html1.mh-extra.com/html/freescale-semiconductor/mcf54455/mcf54455_reference-manual_2330541578.webp)
Advanced Technology Attachment (ATA)
Freescale Semiconductor
23-3
The PIO mode is a slow protocol, mainly intended to program the ATA disc drive, but also possible
to transfer data to/from the disc drive. During PIO mode, the FIFO is not active.
•
DMA Mode
In DMA mode, data transfers between the ATA bus and the FIFO. Two different DMA protocols
are supported on the ATA bus: ultra DMA mode and multiword DMA mode. Acontrol register bit
selects which DMA mode.
A DMA transfer starts when DMA mode transfer is enabled by writing some control bit and when
the drive connected to the ATA bus pulls its DMARQ signal high.
During an ATA bus DMA transfer, data transfers between the ATA bus and the FIFO. The transfer
pauses to avoid FIFO overflow and FIFO underflow.
The host CPU or the host smart DMA unit must read data or write data to the FIFO to keep the
transfer going. Normally, the host (smart) DMA unit takes on this task. For this purpose, the FIFO
receive/transmit alarms are sent to the host DMA unit. The FIFO receive alarm informs the host
DMA unit of at least one packet of data waiting in the FIFO to be read by the host DMA. When
this alarm is asserted, the host DMA should transfer one packet of data from FIFO to the main
memory. Typical packet size is 32 bytes (8 longwords), but other packet sizes can be managed too.
FIFO transmit alarm informs the host DMA unit of space for at least one packet to be written by
the host DMA. When this alarm is asserted, the host DMA must transfer one packet of data from
main memory to the FIFO. Typical packet size is 32 bytes (8 longwords), but other packet sizes
can be managed too.
23.2
External Signal Description
for the list of signals entering and exiting this module to peripherals within the device.
Table 23-1. ATA Signal Properties
Name
Function
Reset State
I/O
ATA_RESET
ATA bus reset signal
1
1
This signal is a standard ATA bus signal. It conforms with the ATA specification.
0
O
ATA_DIOR
ATA bus read strobe
1
O
ATA_DIOW
ATA bus write strobe
1
O
ATA_CS[1:0]
ATA bus chip selects
1
O
ATA_DA[2:0]
ATA bus address line
0
O
ATA_DMARQ
ATA bus DMA request
—
I/O
ATA_DMACK
ATA bus DMA acknowledge
1
O
ATA_INTRQ
ATA bus interrupt request
—
I/O
ATA_IORDY
ATA bus I/O channel ready
—
O
ATA_DATA[15:0]
ATA data bus (little-endian)
Hi-Z
Tri-state I/O
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 ...