Integrator's Manual GR47/GR48

5. SYSTEM CONNECTOR INTERFACE
38
LZT 123 7589 R1A
5.9.3 Control Signals - RTS, CTS, DTR, DSR, DCD, RI
UART1 control signals are active low and need a standard interface IC,
such as the MAX3237, to generate standard RS232 levels.
UART1 converted signals, together with DGND, RD and TD form a
9-pin RS232 data port.
RTS and CTS are capable of transmitting at 1/10
th
of the data transmission
speed for data rates up to 460 kbit/s (byte-oriented flow control
mechanism).
1RWH When hardware flow control is not used in communications between the
application and the radio device, RTS and CTS must be connected to each
other at the radio device.
Switching times for RTS and CTS
The table below shows the switching times.
Request to Send (RTS)
Used to condition the DCE for data transmission. The default level is high
by internal pull up.
The application must pull RTS low to enable data transmission from the
radio device. Similarly, the radio device asserts CTS low, indicating it is
ready to receive data transmission from the host.
Clear To Send (CTS)
CTS is asserted by the DCE to indicate that the host (DTE) may transmit
data. When CTS is high, the host (DTE) is not permitted to transmit data.
The table below shows the load characteristics for this signal.
Parameter Limit
Time from Low to High level < 2 µs
Time from High to Low level < 2 µs
Parameter Limit
Application driving impedance < 100 Ω
Input capacitance < 2 nF
Input resistance (pull-up) 100 kΩ to DGND
Parameter Limit
Application load capacitance < 500 pF
Application load resistance ≥ 1 MΩ