I/O Buffer Sourcing And Sinking Limit; Bus Loading - Rabbit RabbitCore RCM4200 User Manual

A.3 I/O Buffer Sourcing and Sinking Limit
Unless otherwise specified, the Rabbit I/O buffers are capable of sourcing and sinking
8 mA of current per pin at full AC switching speed. Full AC switching assumes a
29.4 MHz CPU clock with the clock doubler enabled and capacitive loading on address
and data lines of less than 70 pF per pin. The absolute maximum operating voltage on all
I/O is 3.6 V.
A.4 Bus Loading
You must pay careful attention to bus loading when designing an interface to the
RCM4200. This section provides bus loading information for external devices.
Table A-5 lists the capacitance for the various RCM4200 I/O ports.
Table A-5. Capacitance of Rabbit 4000 I/O Ports
Parallel Ports A to E
Table A-6 lists the external capacitive bus loading for the various RCM4200 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-6.
Table A-6. External Capacitive Bus Loading -40°C to +85°C
Output Port
All I/O lines with clock
doubler enabled
Table A-7 lists the loadings for the A/D converter inputs.
User's Manual
I/O Ports
Clock Speed
(MHz)
58.98
Table A-7. A/D Converter Inputs
Parameter
Input Capacitance
Input Impedance
Input
Capacitance Capacitance
(pF)
12
Maximum External
Capacitive Loading (pF)
100
Value
4–9.7 pF
Common-Mode 6 MΩ
Differential 7 MΩ
Output
(pF)
14
95