5.5 Ultra DMA Feature Set
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.
5.5.6Series 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 5.28 Recommended series termination for Ultra DMA
Signal | Host Termination | Device Termination |
|
|
|
| 22 ohm | 82 ohm |
|
|
|
| 22 ohm | 82 ohm |
|
|
|
33 ohm | 82 ohm | |
|
|
|
DA0, DA1, DA2 | 33 ohm | 82 ohm |
|
|
|
DMACK- | 22 ohm | 82 ohm |
|
|
|
DD15 through DD0 | 33 ohm | 22 ohm |
|
|
|
DMARQ | 82 ohm | 22 ohm |
|
|
|
INTRQ | 82 ohm | 22 ohm |
|
|
|
| 82 ohm | 22 ohm |
|
|
|
RESET- | 33 ohm | 82 ohm |
|
|
|
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
Vcc