Encoder Mode
CTA88 can be put into Encoder Mode by connecting TX/RX MODE (pin 4) to supply (Vcc)
+5V
supply
A7
A6
A5
A4
A3
A2
A1
A0
Vdd
RST
TXD
TXE
RF
TXD
EN
TX MODE
C0
Vcc
C1
C2
GND
Vss
OSC1
OSC2
D0
10k array
100nF
Vss
D7
D6
D5
D4
3.58MHz
D1
D2
D3
10k array
10k array
Figure 2: CTA88 in Encoder Mode
Input/Output Description
Pin
Name
1
2
3
4
5
6
RST
TXD
TXE
TX/RX MODE
C0
Input
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
Output
Output
Input
Input
Input
Operating mode inputs5
C1
7
C2
Input
8
9
Vss
Supply
Output
Input
Input
Supply
Supply
Supply Ground
OSC1
OSC2
D0 - D7
Vss
Connect to 3.58MHz resonator1
Connect to 3.58MHz resonator1
8 bits of Data input (no internal pull-ups)4
Supply Ground
10
11 - 18
19
20
Vdd
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
21 - 28
A0 – A7
Input
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
RADIOMETRIX [ RADIOMETRIX LTD ]
