User`s manual

64 RabbitCore RCM2100
A.2 Bus Loading
You must pay careful attention to bus loading when designing an interface to the Rabbit-
Core RCM2100. This section provides bus loading information for external devices.
Table A-2 lists the capacitance for the various RCM2100 I/O ports.
Table A-3 lists the external capacitive bus loading for the various RCM2100 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-2. Capacitance of RCM2100 I/O Ports
I/O Ports
Input Capacitance Output Capacitance
Typ. Max. Typ. Max.
Parallel Ports A to E 6 pF 12 pF 10 pF 14 pF
Data Lines BD0–BD7 12 pF 18 pF 18 pF 22 pF
Address Lines BA0–BA12 — — 8 pF 12 pF
Table A-3. External Capacitive Bus Loading -40°C to +70°C
Output Port
Clock Speed
(MHz)
Maximum External
Capacitive Loading (pF)
A[12:0]
D[7:0]
22.1 50
PD[3:0] 22.1 100
PA[7:0]
PB[7,6]
PC[6,4,2,0]
PD[7:4]
*
PE[7:0]
* The Parallel Port D outputs (PD[7:4]) are available only on the
RCM2120 and the RCM2130 models.
22.1 90
All data, address, and I/O
lines with clock doubler
disabled
11.0592 100