Ultra Dma Crc Rules - Fujitsu MPF3XXXAT Product Manual

11) The device shall compare the CRC data received from the host with the results of its
own CRC calculation. If a miscompare 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 (see 5.5.5).
12) The device shall release DDMARDY- within t
13) The host shall neither negate STOP nor HSTROBE until at least t
DMACK-.
14) The host shall not assert DIOW-, CS0-, CS1-, DA2, DA1, or DA0 until at least t
after negating DMACK.
5.5.5

Ultra DMA CRC rules

The following is a list of rules for calculating CRC, determining if a CRC error has occurred
during an Ultra DMA burst, and reporting any error that occurs at the end of a command.
a) Both the host and the device shall have a 16-bit CRC calculation function.
b) Both the host and the device shall calculate a CRC value for each Ultra DMA burst.
c) The CRC function in the host and the device shall be initialized with a seed of 4ABAh at
the beginning of an Ultra DMA burst before any data is transferred.
d) For each STROBE transition used for data transfer, both the host and the device shall
calculate a new CRC value by applying the CRC polynomial to the current value of their
individual CRC functions and the word being transferred. CRC is not calculated for the
return of STROBE to the asserted state after the Ultra DMA burst termination request has
been acknowledged.
e) At the end of any Ultra DMA burst the host shall send the results of its CRC calculation
function to the device on DD (15:0) with the negation of DMACK-.
f) The device shall then compare the CRC data from the host with the calculated value in its
own CRC calculation function. If the two values do not match, the device shall save the
error and report it at the end of the command. A subsequent Ultra DMA burst for the same
command that does not have a CRC error shall not clear an error saved from a previous
Ultra DMa burst in the same command. If a miscompare 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.
g) For READ DMA or WRITE DMA commands: When a CRC error is detected, it shall be
reported by setting both ICRC and ABRT (bit 7 and bit 2 in the Error register) to one.
ICRC is defined as the "Interface CRC Error" bit. The host shall respond to this error by
re-issuing the command.
h) A host may send extra data words on the last Ultra DMA burst of a data out command. If
a device determines that all data has been transferred for a command, the device shall
terminate the burst. A device may have already received more data words than were
required for the command. These extra words are used by both the host and the device to
calculate the CRC, but, on an Ultra DMA data out burst, the extra words shall be discarded
by the device.
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after the host has negated DMACK-.
IORDYZ
C141-E099-01EN
after negating
ACK
ACK