dp83902a National Semiconductor Corporation, dp83902a Datasheet - Page 48

• Manufacturer Part Number: dp83902a
• Description: St-nictm Serial Network Interface Controller For Twisted Pair
• Manufacturer: National Semiconductor Corporation

13 0 Bus Arbitration and Timing
An additional caution for high speed systems is that the
polling must follow guidelines specified in the Time Between
Chip Selects section That is there must be at least 4 bus
clocks between chip selects (For example when BSCK
20 MHz then this time should be 200 ns)
The general flow for executing a Remote Write is
1 Set Remote Byte Count to a value
2 Issue the ‘‘dummy’’ Remote Read command
Note The dashed lines indicate incorrect timing as described in text
Address to unused RAM (one location before the trans-
mit start address is usually a safe location)
l
1 and Remote Start
Timing Diagram for Dummy Remote Read
(Continued)
e
48
3 Read the Current Remote DMA Address (CRDA) (both
4 Compare to previous CRDA value if different go to 6
5 Delay and jump to 3
6 Set up for the Remote Write command by setting the
7 Issue the Remote Write command
bytes)
Remote Byte Count and the Remote Start Address (note
that if the Remote Byte count in step 1 can be set to the
transmit byte count plus one and the Remote Start Ad-
dress to one less these will now be incremented to the
correct values )
TL F 11157 – 62