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
RADIOMETRIX [ RADIOMETRIX LTD ]
