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DNT900 - 08/16/10
Sleep is also affected by the following registers associated with I/O reporting: IO_ReportTrigger,
IO_ReportInterval, ADC_SampleIntvl, and GPIO_EdgeTrigger. The following table indicates how the
status, control and PWM pins function on sleeping remotes:
Pin
Awake
Sleep
/HOST_RTS
Normal operation
high impedance
/HOST_CTS
Normal operation
0 V
/DCD
Normal operation
0 V
ACT
3 V
0 V
DIVERSITY
Normal operation
0 V
RADIO_TXD Normal
operation
Hi-Z
RADIO_RXD
Normal operation
0 V
PWM0
Normal operation
0 V
PWM1
Normal operation
0 V
Table 2.15.1
Note that the ACT pin may be used by a local host to detect when a sleeping remote is awake. The
behavior of the GPIOs during sleep is governed by the GPIO_ SleepMode, GPIO_SleepDir, and
GPIO_SleepState configuration registers. Refer to the register definitions in Section 4.2.
2.16 Encryption
The DNT900 supports 128-bit AES encryption of data and configuration packets. Encryption is enabled
by setting the EncryptionKey register to a value other than a string of null (0x00) bytes. A remote without
encryption enabled cannot link to an encrypted base, and an encrypted remote will not attempt to link to
an unencrypted base. A remote's encryption key must match that of the base before it can link. The
EncryptionKey register can be set over the air so it can be changed periodically if desired. Once an
encryption key has been entered, it can be changed but it cannot be read back.
2.17 Synchronizing Co-located Bases
The EX_SYNC input (Pin 15) on the DNT900 allows co-located bases to synchronize their transmissions
so they all transmit at the same time. This prevents the situation where one base is transmitting while
another nearby base is trying to hear a distant remote. Even though the base radios may be on different
frequencies, because of their close proximity, the transmitting base can reduce the receiving base’s ability
to hear distant remotes. The EX_SYNC input has the following characteristics:
1. Base radios trigger on the rising edge of the pulse applied to their EX_SYNC input.
2. All co-located bases must use the same hop duration and the period of the pulse train applied to
the EX_SYNC input must be within ±10 µs of this hop duration.
3. The co-located bases must use different network IDs but the same frequency subband, which as-
sures they are using different hopping patterns.
4. A pulse of 50 to 800 µs triggers base beacon synchronization. A train of pulses as described
above will synchronize a group of co-located base stations after a period of time.
Note that co-located base synchronization cannot be used with tree-routing systems.
