Bus Loading - Rabbit RabbitCore RCM3400 User Manual

A.2 Bus Loading
You must pay careful attention to bus loading when designing an interface to the
RCM3400. This section provides bus loading information for external devices.
Table A-2 lists the capacitance for the various RCM3400 I/O ports.
Table A-2. Capacitance of Rabbit 3000 I/O Ports
Parallel Ports A to G
Table A-3 lists the external capacitive bus loading for the various RCM3400 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 +85°C
Output Port
All I/O lines with clock
doubler enabled
All I/O lines with clock
doubler disabled
Table A-4 lists the loadings for the A/D converter inputs.
User's Manual
I/O Ports
Clock Speed
(MHz)
29.4
14.7456
Table A-4. A/D Converter Inputs
Parameter
Input Capacitance
Input Impedance
Input
Capacitance Capacitance
(pF)
12
Maximum External
Capacitive Loading (pF)
70
100
Value
4–9.7 pF
Common-Mode 6 MΩ
Differential 7 MΩ
Output
(pF)
14
63