SYSTEM CONNECTOR INTERFACE
39
LZT 123 8020 R1A
Serial Data To Radio Device (TD)
TD is an input signal, used by the application to send data via
UART1 to the radio device.
Parameter Limit
Application driving impedance
<
100
Ω
Input capacitance
1nF
Input resistance
100 k
Ω
to 2.75 V
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 9pin 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 (byteoriented
flow control mechanism).
Note!
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.
Parameter Limit
Time from Low to High level
<
2
µs
Time from High to Low level
<
2
µs
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.
Parameter Limit
Application driving impedance
< 100
Ω
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