Z-World RabbitLink EG2100, Руководство пользователя

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30 RabbitLink (EG2100)
The programming port, which is shown in Figure E-1, can serve as a convenient communications
port for field setup or other occasional communication need (for example, as a diagnostic port). 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 performed to start
execution of a special program dedicated to this functionality.
Figure E-1. Programming Port Pin Assignments
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 pro-
gramming 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 connected 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 spurious 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 signal 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 programming port is for the cable to connect TXA to
one of the SMODE pins and then test for the connection by raising PC6 (by configuring it as a gen-
eral output bit) and reading the SMODE pin after the cold-boot mode has been disabled.
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