CY4636 WirelessUSB™ LP Keyboard Mouse Reference Design Kit User Guide, Doc. # 001-70355 Rev. *A
101
A.3.8
Protocol Modes
The ping, idle, reconnect, bind, and data modes are discussed in this section.
A.3.8.1
Ping Mode (Bridge Only)
Ping Mode is used by the bridge to find an available channel; channels are unavailable if they are
being used by another network with the same PN code, or if there is excessive noise on the channel.
The bridge first listens for activity on the selected channel. If the channel is inactive the bridge alter-
nately transmits Pings and listens for Ping Responses for a defined* period of time. During Ping
Mode the bridge also checks the Receive Signal Strength Indicator (RSSI) of the radio in order to
determine if a non-WirelessUSB device is using this channel (or a WirelessUSB device on the same
channel using a different PN code). If a Ping Response is received, indicating that another bridge is
using this channel the bridge selects the next channel using the Channel Selection Algorithm and
repeat this procedure. The bridge also selects another channel using the Channel Selection Algo-
rithm if RSSI is high; this indicates that there are other RF sources on the channel. If a Ping
Response is not received and RSSI is low, the bridge assumes the channel is available and moves
to Data Mode. Bridges send Ping Responses in response to all received Pings if the bridge is in Data
Mode. HIDs never respond to Pings.
[*The timeout value is configurable using the PING_NUM_RSSI define.]
A.3.8.2
Idle Mode (HID only)
This is the state of an HID after a power-on reset before it has had any communication with the Wire-
lessUSB bridge. If the bridge's MID is stored in nonvolatile memory the HID retrieves the bridge's
MID, calculate the Network ID and move to Reconnect Mode. If the bridge's MID is not stored in non-
volatile memory the HID waits in Idle Mode until a user-initiated event causes the HID to enter Bind
Mode. After a defined period of time in Idle Mode the HID enters Sleep Mode in order to conserve
power. When the HID wakes up due to a user action, it re-enters Idle Mode.
A.3.8.3
Reconnect Mode (HID only)
Reconnect Mode is used by the HID to discover the current channel used by the bridge and to estab-
lish a connection with the bridge. Upon entering Reconnect Mode the HID uses the Network ID to
select a channel using the Channel Selection Algorithm. The HID transmits Connect Requests con-
taining the Manufacturing ID of the desired bridge and listens for an AutoACK. If an AutoACK is
received the HID disables the AutoACK and continues to listen for a Connect Response. If a bridge
in Data Mode receives a Connect Request containing its Manufacturing ID, it sends a positive Con-
nect Response to the HID. If a HID receives a positive Connect Response it moves to Data Mode. If
a HID does not receive a positive Connect Response, it selects the next channel using the Channel
Selection Algorithm and repeats the procedure. If the HID does not receive a positive Connect
Response on any of the channels in the subset, it enters Sleep Mode in order to conserve power.
When the HID wakes up due to a user action it reenters Reconnect Mode.
A.3.8.4
Bind Mode
HID.
Bind Mode allows the HID to retrieve the bridge's Manufacturing ID which is used to calculate
the Network ID. Upon entering Bind Mode the HID sets the current channel and PN code to the
channel and PN code specified in the Bind ID. The HID then transmits Bind Requests and listens for
an AutoACK. If an AutoACK is received, the HID (keeping the AutoACK enabled) continues to listen
for a Bind Response (containing the bridge's MID) from the bridge. If a Bind Response is not
received the HID moves to the next channel. If a Bind Response is received the HID stores the
bridge's MID, calculates the Network ID and moves to Reconnect Mode. The algorithms used to cal-
culate these fields are implementation specific and should be the same on the bridge and the HID
(both devices use the bridge's Manufacturing ID to calculate these fields). If a defined* period of time
