Digi BL1800 user manual Programming Port, 485 R16

The Jackrabbit comes with a 220 Ω termination resistor and 681 Ω bias resistors already installed, as shown in Figure 12.

bias	R18
	681 W	6
485+
	R17
termination
	220 W	7
485–	R16
bias
	681 W

U6

U1

GND	J1
	J2
VIN GND

J3

J4

GND	VCC
PA0	PA1
PA2	PA3					U5
PA4	PA5
PA6	PA7	U3
GND	GND
PB0	PB1
PB2	PB3
PB4	PB5
PB6	PB7		Rabbit		2000
WDO	PCLK
GND	PE7
PE6	PE5
PE4	PE3
PE2	PE1
PE0	GND
HV0	HV1
HV2	HV3
K	+RAW
GND	VCC			Y3

JACKRABBIT Z-World, Inc.

U4
-232		J5
RS
	VCC	GND
	RXB	RXC
	TXB	TXC
	PC0	PC1
	PC2	PC3
SRAM	PC4	PC5
	PC6	PC7
	AD0	AGND
	DA0	DA1
	PD0	PD1
	PD2	PD3
	PD4	PD5
	PD6	PD7
R16	GND	GND
	485–	485+
U6	VCC	VCC
	SM0	SM1
	IOBEN	STAT
RS-485	GND	VBAT
	/RST	GND
R18		RESET
	R17

Figure 12. 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.

3.5.3 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. Dynamic C uses the programming port to download and debug programs.

The programming port is also used for the following operations.

•Cold-boot the Rabbit 2000 after a reset.

•Remotely download and debug a program over an Ethernet connection using the RabbitLink EG2110.

•Fast copy designated portions of flash memory from one Rabbit-based board (the master) to another (the slave) using the Rabbit Cloning Board.

Alternate Uses of the Serial Programming Port

All three clocked Serial Port A signals are available as

•a synchronous serial port

•an asynchronous serial port, with the clock line usable as a general CMOS input

The serial programming port may also be used as a serial port via the DIAG connector on the serial programming cable.

30 Jackrabbit (BL1800)