RabbitCore RCM2200, Руководство пользователя

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C–2 Programming Cable RabbitCore RCM2200
The programming port, which is shown in Figure C–1,
can serve as a convenient communications port for
field setup or other occasional communication need
(for example, as a diagnostic port). There are sev-
eral ways that the port can be automatically inte-
grated into software. If the port is simply to perform a setup function, that is, write setup information to
flash memory, then the controller can be reset
through the programming port and a cold boot per-
formed to start execution of a special program dedi-
cated to this functionality.
When the
PROG
connector is used, the /RESET
line can be asserted by manipulating DTR and the
STATUS line can be read as DSR on the serial port.
The target can be restarted by pulsing reset and then,
after a short delay, sending a special character string
at 2400 bps. To simply restart the BIOS, the string
80h, 24h, 80h can be sent. When the BIOS is
started, it can tell whether the programming cable is
connected because the SMODE1 and SMODE0
pins are sensed as being high. This will cause the
Rabbit 2000 to enter the bootstrap mode. The
Dynamic C programming mode then can have an
escape message that will enable the diagnostic serial
port function.
Alternatively, the DIAG connector can be used to
connect the programming port. The /RESET line
and the SMODE1 and SMODE0 pins are not con-
nected to this connector. The programming port is
then enabled as a diagnostic port by polling the port
periodically to see if communication needs to begin
or to enable the port and wait for interrupts. The
pull-up resistors on RXA and CLKA prevent spuri-
ous data reception that might take place if the pins
floated.
If the clocked serial mode is used, the serial port can
be driven by having two toggling lines that can be
driven and one line that can be sensed. This allows
a conversation with a device that does not have an
asynchronous serial port but that has two output sig-
nal lines and one input signal line.
The line TXA (also called PC6) is zero after reset if
the cold-boot mode is not enabled. A possible way
to detect the presence of a cable on the program-
ming port is for the cable to connect TXA to one of
the SMODE pins and then test for the connection by
raising PC6 and reading the SMODE pin after the
cold-boot mode has been disabled.
Figure C–1:
Programming Port Pin Assignments
10
1 2
3 4
5 6
7 8
9
PROGRAMMING PORT PIN ASSIGNMENTS
(Rabbit PQFP pins are shown in parenthesis)
1. RXA (51)
2. GND
3. CKLKA (94)
4. +5 V/+3 V
5. /RESET
6. TXA (54)
7. n.c.
8. STATUS (output) (38)
9. SMODE0 (36)
10. SMODE1 (35)
~50 k W
GND
~50 k W
+
~50 k W
GND
~50 k W
+
~10 k W
+
Programming Port
Pin Numbers