Specifications

BASIC Stamp II

Parallax, Inc. • BASIC Stamp Programming Manual 1.8 • Page 325

This is to ensure that the sender sees a stop signal (0 for inverted comms)

when the receiver is being programmed.

Flow-control Timeout

Flow control solves one problem but can create another—if the receiver

isn’t connected, Serout may never get permission to send. The pro-

gram will be stuck in Serout indefinitely. To prevent this, Serout allows

you to specify how long it should wait for permission, from 0 to 65535

ms. If the specified time passes without permission to send, Serout

aborts, allowing the program to continue at tlabel. Here’s the previous

example (just the Sender code) with a 2.5-second timeout:

Serout 1\0,16468,2500,noFlow["HELLO!"]

' ...instructions executed after a successful Serout

stop

noFlow:

' If Serout times-out waiting for flow-control permission,

' It jumps to this label in the program.

Networking with Open Baudmodes

The open baudmodes can be used to connect multiple BS2s to a single

pair of wires to create a party-line network. Open baudmodes only

actively drive the Serout pin in one state; in the other state they discon-

nect the pin. If BS2s in a network used the always-driven baudmodes,

two BS2s could simultaneously output opposite states. This would cre-

ate a short circuit from +5V to ground through the output drivers of

the BS2s. The heavy current flow would likely damage the BS2s (and it

would certainly prevent communication). Since the open baudmodes

only drive in one state and float in the other, there’s no chance of this

kind of short.

The polarity selected for Serout determines which state is driven and

which is open, as follows:

— Polarity — Resistor

State Inverted Noninverted Pulled to

0 open driven GND

1 driven open +5V