22
Jackrabbit (BL1800)
The Jackrabbit comes with a 220
Ω
termination resistor and 681
Ω
bias resistors already
installed, as shown in Figure 10.
Figure 10. RS-485 Termination and Bias Resistors
The load these bias and termination resistors present to the RS-485 transceiver (U6) limits
the number of Jackrabbits in a multidrop network to one master and nine slaves, unless the
bias and termination resistors are removed. When using more than 10 Jackrabbits in a
multidrop network, leave the 681
Ω
bias resistors in place on the master Jackrabbit, and
leave the 220
Ω
termination resistors in place on the Jackrabbit at each end of the network.
2.5.3 Programming Port
The Jackrabbit has a 10-pin program header labeled J3. The programming port uses the
Rabbit 2000’s serial port A for communication. The Rabbit 2000 startup-mode pins
(SMODE0, SMODE1) are presented to the programming port so that an externally con-
nected device can force the Jackrabbit to start up in an external bootstrap mode.
The programming port is used to start the Jackrabbit in a mode where the Jackrabbit will
download a program from the port and then execute the program. The programming port
transmits information to and from a PC while a program is being debugged.
The Jackrabbit can be reset from the programming port.
The Rabbit 2000 status pin is also presented to the programming port. The status pin is an
output that can be used to send a general digital signal.
The clock line for serial port A is presented to the programming port, which makes fast
serial communication possible.
U6
R18
681
W
R17
220
W
R16
681
W
485+
485
6
7
R16
termination
bias
bias
R17
R18
U4
VIN
GND
GND
RESET
JACKRABBIT Z-World, Inc.
GND
PA0
PA2
PA4
PA6
GND
PB0
PB2
PB4
PB6
WDO
GND
PE6
PE4
PE2
PE0
HV0
HV2
K
GND
VCC
PA1
PA3
PA5
PA7
GND
PB1
PB3
PB5
PB7
PCLK
PE7
PE5
PE3
PE1
GND
HV1
HV3
+RAW
VCC
GND
RXC
TXC
PC1
PC3
PC5
PC7
AGND
DA1
PD1
PD3
PD5
PD7
GND
485+
VCC
SM1
STAT
VBAT
GND
VCC
RXB
TXB
PC0
PC2
PC4
PC6
AD0
DA0
PD0
PD2
PD4
PD6
GND
485
VCC
SM0
IOBEN
GND
/RST
J5
U6
U5
U3
J4
U1
J1
J2
J3
Y3
Rabbit 2000
SRAM
RS-232
RS-485
Содержание BL1800
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Страница 31: ...User s Manual 27 APPENDIX A SPECIFICATIONS Appendix A provides the specifications for the Jackrabbit ...
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