
A.2 Bus Loading
You must pay careful attention to bus loading when designing an interface to the
RCM3000. This section provides bus loading information for external devices.
Table A-2 lists the capacitance for the various RCM3000 I/O ports.
Table A-2. Capacitance of Rabbit 3000 I/O Ports
Input
Output
I/O Ports
Parallel Ports A to G
Capacitance
(pF)
12
Capacitance
(pF)
14
Table A-3 lists the external capacitive bus loading for the various RCM3000 output ports.
Be sure to add the loads for the devices you are using in your custom system and verify
that they do not exceed the values in
Table A-3.Table A-3. External Capacitive Bus Loading -40°C to +70°C
54
Output Port
All I/O lines with clock
doubler enabled
All I/O lines with clock
doubler disabled
Clock Speed
(MHz)
29.4
14.7456
Maximum External
Capacitive Loading (pF)
30–70
100
RabbitCore RCM3000