i) The CRC generator polynomial is : G (X) = X16 + X12 + X5 + 1.
Note: Since no bit clock is available, the recommended approach for calculating CRC is to
use a word clock derived from the bus strobe. The combinational logic shall then be
equivalent to shifting sixteen bits serially through the generator polynomial where DD0 is
shifted in first and DD15 is shifted in last.
5.5.6
Series termination required for Ultra DMA
Series termination resistors are required at both the host and the device for operation in any of the
Ultra DMA Modes. The following table describes recommended values for series termination at
the host and the device.
Table 5.16 Recommended series termination for Ultra DMA
DIOR-:HDMARDY-:HSTROBE
DIOW-:STOP
CS0-, CS1-
DA0, DA1, DA2
DMACK-
DD15 through DD0
DMARQ
INTRQ
IORDY:DDMARDY-:DSTROBE
RESET-
Note: Only those signals requiring termination are listed in this table. If a signal is
not listed, series termination is not required for operation in an Ultra DMA Mode.
For signals also requiring a pull-up or pull-down resistor at the host see Figure 5.7.
Figure 5.7
Signal
Host Termination
Vcc
Ultra DMA termination with pull-up or pull-down
C141-E110-02EN
Device Termination
22 ohm
82 ohm
22 ohm
82 ohm
33 ohm
82 ohm
33 ohm
82 ohm
22 ohm
82 ohm
33 ohm
33 ohm
82 ohm
22 ohm
82 ohm
22 ohm
82 ohm
22 ohm
33 ohm
82 ohm
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