Operating modes
Device operation is set up by a 3 bit word, on the C0-C2 inputs.
TX / Encoder modes
000
Device is inactive
001
Send single burst, once only (on reset, and on each C0 low/high transition)
010
Send continuously
011
Send single burst on any change of Data input word
100
Send continuously while any Data input pin is high
101
Send a burst on average every 1.75 seconds. A P/N sequence generates a delay of 1 -
2.5s between bursts
110
Serial mode (see notes)
111
Transmitter test. Send a constant 250Hz squarewave (C0=H, C1=H, C2=H)
RX / Decoder modes
000
Local test. Data output word equals Address input word
001
Output last data received (150mS timeout)
010
Output last data (3 second timeout: see notes)
011
Hold last data received
100
D0-3 'set' corresponding bit, D4 resets D0, D5 resets D1 .. and so on
101
A '1' on any bit toggles the state of the corresponding output pin
110
Serial (see notes)
111
Link test. Data word outputs most recently received burst address
Which modes to use?
The CTA88 have a variety of operating modes. These are better understood by relating them to different
applications:
1.
Wire replacment:.
Operate transmitter in mode 010 (continuous: allows the STB output to be used
as a 'good link' indicator) and receiver in mode 001.
If receiver operates in latched (011) mode then 'chattering' of the output is reduced (at extreme range,
or with interferers present), but the link is no longer fail safe
Latched mode is also compatible with send on change (011)
2.
Momentary push buttons:
Transmitter in mode 100 (send while any input is high), receiver in 001.
Outputs remain high for as long as the button is held down. This is the mode one would choose to
control (for instance) a pan/tilt head (D0= slew left, D1 = slew right, etc)
3.
Controlling four lights:
Use transmit mode 100 (send while high) or 011 (send on change), with the
receiver in mode 100. This gives four outputs (D0-D3), each set by one transmitter input (D0-D3) and
reset by another (D4-D7)
4.
Monitoring infrequent events
(such as door open/shut): Use transmitter in periodic transmit (101,
to keep channel occupancy and power usage low), and receiver on 010 (3 second timeout), 011 (hold last
burst) or 110 (serial data output, to a PC or data logging device).
In this mode the transmit duty cycle is less than 10% on average, and the variable delay between bursts
permits same channel operation of several CTA88 links with minimum transmit collisions
5.
Send burst on trigger event:
Set transmitter to mode 000 (off) and use C0 line high as a 'strobe'
line. A pulse between 100uS and 25mS with initiate a single transmission.
This gives an idea of the usable combinations, but with a little imagination others will be found
Radiometrix Ltd
CTA88
page 4
RADIOMETRIX [ RADIOMETRIX LTD ]
