Data Sheet

AC4790
Datasheet
https://www.lairdconnect.com/
10
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Pin #
1x1 Pin
Type
Signal Name
Function
15
16
I
UP_RESET
RESET – Controlled by the AC4790 for power-on reset if left
unconnected. After a stable power-on reset, a logic High pulse will
reset the transceiver.
16
13
GND
GND
Signal Ground
17
17
I
CMD/Data
When logic Low, the transceiver interprets OEM host data as
command data. When logic High, the transceiver interprets OEM
host data as transmit data.
18
15
3
I
AD In
10 bit Analog Data Input
19
1,8,20
24-28
N/C
Do Not Connect
Has internal connection, for Laird use only.
20
18
O
Session Status
When logic Low, the transceiver is in session
N/A
14
RF
RF Port
RF Interface
N/A
22
I
Reset
Active Low version of UP_RESET. If RESET is used, UP_RESET
should be left floating and if UP_RESET is used, RESET should
be left floating.
1. When ordered with a RS485 interface (not available on the AC4790-1x1).
2. Must be tied to VCC or GND if not used. Should never be permitted to float.
3. If used, requires a shunt 0.1μF capacitor at pin 15 followed by a series 1k resistor.
4.2 Detailed Pin Definitions
4.2.1 Generic I/O
Both GI0 and GI1 pins serve as generic input pins. When Protocol Status (byte 0xC2 of EEPROM) is disabled, GO0 & GO1
serve as generic outputs. When Protocol Status is enabled, pins GO0 and GO1 alternatively serve as the Session Status and
Receive Acknowledge Status pins, respectively. Reading and writing of these pins can be performed using CC Commands.
4.2.1.1 Hardware Protocol Status
When the GO0 pin is configured as the Session Status pin, GO0 is normally Low. GO0 will go High when a session is initiated
and remain High until the end of the session. When the GO1 pin is configured as the Receive Acknowledge Status pin, GO1 is
normally Low and GO1 will go High upon receiving a valid RF Acknowledgement and will remain High until the end (rising
edge) of the next hop.
4.2.2 TXD & RXD
Serial TTL
The AC4790-200 accepts 3.3 or 5VDC TTL level asynchronous serial data on the RXD pin and interprets
that data as either Command Data or Transmit Data. Data is sent from the transceiver, at 3.3V levels, to the
OEM host via the TXD pin.
Note: The AC4790-1000 & AC4790-1x1 transceivers only accept 3.3V level signals.
RS485
When equipped with an onboard RS485 interface chip, TXD and RXD become the Half Duplex RS485 pins.
The transceiver interface will be in Receive mode except when it has data to send to the OEM host. TXD is
the non-inverted representation of the data (RS485A) and RXD is a mirror image of TXD (RS485B). The
transceiver will still use RTS (if enabled).
4.2.3 CTS
The AC4790 has an interface buffer size of 256 bytes. If the buffer fills up and more bytes are sent to the transceiver before
the buffer can be emptied, data is lost. The transceiver prevents this loss by asserting CTS High as the buffer fills up and
taking CTS Low as the buffer is emptied. CTS On and CTS Off control the operation of CTS. CTS On specifies the amount of