5.5 Ultra DMA Feature Set
Both the host and device perform a CRC function during an Ultra DMA burst. At the end of an Ultra DMA burst the host sends the its CRC data to the device. The device compares its CRC data to the data sent from the host. If the two values do not match the device reports an error in the error register at the end of the command. If an error occurs during one or more Ultra DMA bursts for any one command, at the end of the command, the device shall report the first error that occurred.
5.5.2 Phases of operation
An Ultra DMA data transfer is accomplished through a series of Ultra DMA data in or data out bursts. Each Ultra DMA burst has three mandatory phases of operation: the initiation phase, the data transfer phase, and the Ultra DMA burst termination phase. In addition, an Ultra DMA burst may be paused during the data transfer phase (see 5.5.3 and 5.5.4 for the detailed protocol descriptions for each of these phases, 5.6 defines the specific timing requirements). In the following rules DMARDY- is used in cases that could apply to either DDMARDY- or
a)An Ultra DMA burst is defined as the period from an assertion of DMACK- by the host to the subsequent negation of
b)A recipient shall be prepared to receive at least two data words whenever it enters or resumes an Ultra DMA burst.
5.5.3 Ultra DMA data in commands
5.5.3.1 Initiating an Ultra DMA data in burst
The following steps shall occur in the order they are listed unless otherwise specifically allowed (see 5.6.3.1 and 5.6.3.2 for specific timing requirements):
1)The host shall keep DMACK- in the negated state before an Ultra DMA burst is initiated.
2)The device shall assert DMARQ to initiate an Ultra DMA burst. After assertion of DMARQ the device shall not negate DMARQ until after the first negation of DSTROBE.
3)Steps (3), (4) and (5) may occur in any order or at the same time. The host shall assert STOP.
4)The host shall negate
5)The host shall negate
6)Steps (3), (4) and (5) shall have occurred at least tACK before the host asserts
