User`s manual

Rabbit 4000 Designer’s Handbook rabbit.com 19
4. How Dynamic C Cold Boots
the Target System
Dynamic C assumes that target controller boards using the Rabbit 4000 CPU have no pre-installed firm-
ware. It takes advantage of the Rabbit 4000’s bootstrap (cold boot) mode, which allows memory and I/O
writes to take place over the programming port.
Figure 4-1 Rabbit Programming Port
The Rabbit programming cable is a smart cable with an active circuit board in its middle. The circuit board
converts RS-232 voltage levels used by the PC serial port to CMOS voltage levels used by the Rabbit
4000. The level converter is powered from the power supply voltage present on the Rabbit 4000 program-
ming connector. Plugging the programming cable into the Rabbit programming connector results in pull-
ing the Rabbit 4000 SMODE0 and SMODE1 (startup mode) lines high. This causes the Rabbit 4000 to
enter the cold boot mode after reset.
RXA
VSS
CLKA
V
DD
/RESET
TXA
STATUS
SMODE0
SMODE1
~50 kW
~50 kW ~50 kW
~5 kW
Vcc
RABBIT 4000
~50 kW
RXA
GND
CLKA
Vcc
/RESET
TXA
n.c.
STATUS
SMODE0
SMODE1
Programming
Header
1
2
3
4
5
6
7
8
9
10
10
12
34
56
78
9
Programming
Header Pinout
Circuit Board with Rabbit 4000 Processor
61
GND
113
+3.3 V
45
62
4
43
42