EW
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Radiometrix
Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP, England
Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233
Issue: 1, 20 December 2007
CTA88
8 bit Address - 8 bit Data encoder/decoder
CTA88 is an 8 bit address, 8 bit data encoder
and decoder combined in a single IC. This
device is intended to be used with ISM band
telemetry modules and can be operated in
either Encode or Decode mode.
CTA88 uses 1kbps differential Manchester bit
balancing with preamble and checksum. It
permits a simple, one way link to be
established, for simple remote control
applications, with a minimum of effort and
no customer software input.
CTA88 is
available in 28pin SO and DIL packages.
Features
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Operating voltage (temperature):
4.0V-5.5V for standard version (-40°C to +125°C)
2.0V-5.5V for low voltage version (-40°C to +85°C)
Draws <2mA without external load
8 bit address and 8 bit data
256 different remotes with 8 controls each
Single packetised transmission for fast activation
Maximum usage of the range capability of an RF module
Adequate preamble to settle data slicer in the receiver.
Extra wake up preamble to allow for transmitter power up time requirements
Differential Manchester encoding of address, data and checksum
Synchronisation codes and checksum to reduce false triggering on noise
Suitable to be used with Narrow Band FM radio modules
Ceramic resonator or crystal oscillator up to 20MHz
Data rate up to 5.6kbps
Minimum external component requirement
Serial operation allow a PC to send or receive CTA88 command bursts
Decoder timeout
Up to 8 encoder/decoder modes including push button, delayed and continuous TX modes.
Figure 1: CTA88 in 28 pin DIL package
Applications
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Security and Alarm systems
Emergency assistance call system
Status reporting and monitoring systems
RF Remote control systems
Industrial controls
HVAC controls
Simple On/Off switching
Long range telecontrol with Narrow Band FM radios
CTA88
page 1
Radiometrix Ltd
Encoder Mode
CTA88 can be put into Encoder Mode by connecting TX/RX MODE (pin 4) to supply (Vcc)
+5V
supply
10k
10k
RF
Transmitter
TXD
EN
Vcc
GND
RST
TXD
TXE
TX MODE
C0
C1
C2
10k array
3.58MHz
Vss
OSC1
OSC2
D0
D1
D2
D3
A7
A6
A5
A4
A3
A2
A1
A0
Vdd
100nF
CTA88
Vss
D7
D6
D5
D4
10k array
10k array
Figure 2: CTA88 in Encoder Mode
Pin
1
2
3
4
5
6
7
8
9
10
11 - 18
19
20
21 - 28
Name
RST
TXD
TXE
TX/RX MODE
C0
C1
C2
Vss
OSC1
OSC2
D0 - D7
Vss
Vdd
A0 – A7
Input/Output
Input
Output
Output
Input
Input
Input
Input
Supply
Output
Input
Input
Supply
Supply
Input
Description
Active Low Reset (Connect to user system reset or tie to Vdd)
Encoded Address and Data to TXD input of RF Transmitter
high (Vdd) = enable radio transmitter module; low (0V) = TX OFF.
tie to Vcc = TX mode
Operating mode inputs
5
Supply Ground
Connect to 3.58MHz resonator
1
Connect to 3.58MHz resonator
1
8 bits of Data input (no internal pull-ups)
4
Supply Ground
4.0V-5.5V supply (decouple with 100nF close to IC).
2.0V-5.5V (low voltage version)
8 bits of Address (Internal pull-ups to Vdd)
4
Notes:
1. OSC1, 2 require a 3.58MHz ceramic resonator like KBR-3.58MKS (internal caps, ground middle
pin).
If a 2 pin resonator or crystal is used, then two 15pF caps are needed : one from OSC1 to 0V ;
one from OSC2 to 0V
2. 'TXE' is active high. For units with TXE inputs, an inverting buffer will be needed
3. Data and Address pins are logic true (1=VCC, 0=0V) inputs and outputs
4. Data inputs have no pullups. Address inputs have weak pullups to Vcc and are schmitt trigger
inputs
5. C0-C2 (pins 5-7) are active high and have no pullups.
6. A 1kbps bi-phase communications protocol is used, compatible with all Radiometrix Wireless
modules
7. A databurst is approximately 110mS long
8. After asserting TX on high (active), the coder allows 50mS for TX to power up and settle
9. Pin 4 (TX/RX MODE) has no pullup.
10.
Without external loads the chip draws less than 2mA from 5v
Radiometrix Ltd
CTA88
page 2
Decoder Mode
CTA88 can be put into Decoder Mode by connecting TX/RX MODE (pin 4) to ground (0V)
+5V
supply
10k
RF
RXD
470R
Receiver
RST
RXD
STB
RX MODE
C0
Vcc
GND
10k array
C1
C2
Vss
OSC1
OSC2
D0
D1
D2
D3
A7
A6
A5
A4
A3
A2
A1
A0
Vdd
Vss
D7
D6
D5
D4
CTA88
100nF
470R
470R
470R
470R
470R
470R
3.58MHz
470R
470R
Figure 3: CTA88 in Decoder Mode
Pin
1
2
3
4
5
6
7
8
9
10
11 - 18
19
20
21 - 28
Name
RST
RXD
STB
TX/RX MODE
C0
C1
C2
Vss
OSC1
OSC2
D0 - D7
Vss
Vdd
A0 – A7
Input/Output
Input
Output
Output
Input
Input
Input
Input
Supply
Output
Input
Output
Supply
Supply
Input
Description
Active Low Reset (Connect to user system reset or tie to Vdd)
baseband DATA from receiver module’s RXD output
Valid data burst detect pulse (36mS long).
tie to Vss = RX mode
Operating mode inputs
4
Supply Ground
Connect to 3.58MHz resonator
1
Connect to 3.58MHz resonator
1
8 bits of Data Outputs
Supply Ground
4.0V-5.5V supply (decouple with 100nF close to IC).
2.0V-5.5V (low voltage version)
8 bits of Address (Internal pull-ups to Vdd)
3
Notes:
1. OSC1, 2 require a 3.58MHz ceramic resonator like KBR-3.58MKS (internal caps, ground middle
pin).
If a 2 pin resonator or crystal is used, then two 15pF caps are needed : one from OSC1 to 0V ;
one from OSC2 to 0V
2. Data and Address pins are logic true (1=VCC, 0=0V) inputs and outputs
3. Address inputs have weak pullups to Vcc and are schmitt trigger inputs
4. C0-C2 (pins 5-7) are active high and have no pullups.
5. A 1kbps bi-phase communications protocol is used, compatible with all Radiometrix Wireless
modules
6. A databurst is approximately 110mS long
7. After asserting TX on high (active), the coder allows 50mS for TX to power up and settle
8. Pin 4 (TX/RX MODE) has no pullup.
9.
Without external loads the chip draws less than 2mA from 5v
Radiometrix Ltd
CTA88
page 3
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
Incompatibilities:
Certain operating modes are not compatible with some of the others:
RX 101 (toggle)
doesn't work with TX 101 (periodic send) as the outputs switch on and off at the send
rate
RX 100 (set and reset)
doesn't work with TX 101 (as the response is sluggish) and doesn't need TX
010 (constant)
RX 101 (toggle) is also not best suited to extreme range operation, where the initiation can be a little
sporadic.
(At extreme range, latched (011) or set/reset (100) are the best receiver modes, combined with TX 100
(send on any '1') as in this mode the failure of any single burst to be received matters less, as the
operator can continue to operate the transmitter until the receiver actuates )
Serial operation:
The CTA88 is capable of a very simple, single byte, serial link operation. It is
selected by a '110' mode input.
This function is mainly intended for diagnostic work in the lab, but it does allow a pc to send or receive
CTA88 command bursts. Address is still selected by the parallel inputs
On the RX:
D4 = 'true' RS232 output
(+ve = low (0), 0V = idle/mark state)
D5 = 'inverted' RS232 output (+ve = idle/'mark' (1) state)
D6 : high for 500uS before, and during, serial byte output
D4 = RS232 input
D5 : low = set 'true' input polarity, high = set 'inverted' input polarity
On the TX
In all cases a single 9600 baud byte is received or sent.
The link is not transparent: on the TX end the 'tx on' pin can be used as a 'busy' output
Timeout:
In modes 001 and 010, the receiver outputs the last received data for a given period, before
resetting D0-D7.
Any subsequent transmission will over-ride the current output state and reset the timer, even if the
timeout period has not expired.
The short period is set to be slightly longer than the time between consecutive transmit bursts in a
continuous mode.
The long timeout is usable with the randomised periodic transmission mode (101), as the 3 second
timeout is longer than the longest delay between transmissions in this mode.
Versions of the chip can be supplied with this period extended to suit customer requirements
Ordering Information:
CTA88-000-SS
CTA88-000-SO
CTA88-000-DIL
CTA88L-000-SS
CTA88L-000-SO
CTA88L-000-DIL
CTA88H-000-SS
CTA88H-000-SO
CTA88H-000-DIL
Standard (≤4MHz)- No Frequency - Shrink Small Outline (SSOP)
Standard (≤4MHz)- No Frequency - Small Outline (SO)
Standard (≤4MHz)- No Frequency - Plastic Dual In Package (PDIP)
Low Voltage (≤4MHz) - No Frequency - SSOP
Low Voltage (≤4MHz) - No Frequency - SO
Low Voltage (≤4MHz) - No Frequency - PDIP
High Speed (4MHz-20MHz) - No Frequency - SSOP
High Speed (4MHz-20MHz) - No Frequency - SO
High Speed (4MHz-20MHz) - No Frequency - PDIP
Radiometrix Ltd
CTA88
page 5
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