CC-2401K2A-CS5 Copeland Communications Inc, CC-2401K2A-CS5 Datasheet - Page 12

• Manufacturer Part Number: CC-2401K2A-CS5
• Description: MODEM 2400BAUD SECURE 5V
• Manufacturer: Copeland Communications Inc

Specifications of CC-2401K2A-CS5

• Data Format: V.21, V.22, V.23, Bell 103
• Baud Rates: 2.4k
• Interface: UART
• Voltage - Supply: 4.2 V ~ 7 V
• Mounting Type: Surface Mount
• Package / Case: Module
• For Use With: 539-1002 - KIT EVALUATION WORLD MODEM II
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 539-1009; CC-2401K2A-CS5

© 2007, Copeland Communications, Inc.
If the host checks the voltage via LVS before initiating a call (or going off-hook for any reason), the modem can
be used to determine if another device is using the telephone line. One way to do this is to verify the voltage in
LVS is above a fixed threshold, such as 30V.
Off-Hook Intrusion Detection
Once a call has begun and the modem is in data mode, the serial port is used for modem data making it
difficult for the host to monitor registers. Therefore, when the modem is off-hook, an algorithm is implemented
to automatically monitor the TIP-RING loop current via the LCS register (SF3). Because the TIP-RING voltage
drops significantly when off-hook, TIP-RING current is a better indicator of another device using the phone
line. The LCS[7:0] bits have a resolution of 1.1mA per bit. An LCS register value of 0x00 indicates less than
the required loop current is present, and a value of 0xff indicates excessive current draw (> 120mA if ILIM = 0
or > 60mA if ILIM = 1). The user can read these bits directly through the LCS register. Upon detecting an
intrusion, an “I” result code is sent to the host if it is in the call negotiation stage or command mode.
Otherwise, the modem can be programmed to generate an interrupt to notify the host of the intrusion.
The off-hook intrusion algorithm monitors the value of LCS (SF3) at a sample rate determined by the DGSR
(SDF, bits 6:0) register (40 ms units). The algorithm compares each LCS sample to the reference value in the
ACL register (S12). If LCS is lower than ACL by an amount greater than DCL (S11, bits 4:0), the algorithm
waits for another LCS sample, and if the next LCS sample is also lower than ACL by an amount greater than
DCL, an interrupt occurs. This helps the modem avoid a false parallel phone detection (PPD) interrupt due to
glitches on the phone line. The ACL is continually updated with the value of LCS as outlined below. The
algorithm can be outlined as follows:
The off-hook intrusion algorithm does not begin to operate immediately after going off-hook. This avoids
accidental interrupts occurring as a result of transients resulting from the modem itself going from on-hook to
off-hook. The time delay between the modem going off-hook and the start of the intrusion algorithm is about 1
second. This can be adjusted using the IST register (S82, bits 7:4).
The off-hook intrusion algorithm may also be disabled for a period of time after dialing begins via the IB
register (S82, bits 2:1). This avoids triggering an interrupt due to pulse dialing, open-switch intervals or line
transients from central office switching. Intrusion can be disabled from the start of dialing to the end of dialing
(IB = Dib), from the start of dialing to the timeout of the IS (S29, bits 7:0) by setting IB = 11. The off-hook
intrusion algorithm is only suspended (not disabled) during this IB interval and sustains through the end of the
interval triggers a PPD interrupt.
Interrupt Detection
The interrupt pin (pin 55) can be programmed to alert the host of loss-of-carrier, loss-of-phone-line
voltage/current, parallel phone detection, and other interrupts listed in the interrupt status mask (S08). After
the host receives an interrupt via the INT# pin, the host should issue the AT:I command. This command
causes a read-clear of the WOR, PPD, NLD, RI, OCD, and REV bits of the S09 register and raises
(deactivates) the INT# pin. All the interrupt status bits in the register S09 remain high after being set until
cleared by the AT:I command.
Loop Current Detection
The CC-2401 can monitor the loss of loop current. This feature can be enabled by setting S08[4] (NLDM) = 1.
This feature is disabled by default. If the loop current is too low for normal DAA operation, S09[4] (NLD) is set.
IF
THEN
IF
THEN
LCS(t) = LCS(t – 40 ms x DGSR)
and
LCS(t) – ACL > DCL
ACL = LCS(t)
(ACL – LCS[t – 40 ms x DGSR]) > DCL)
and
(ACL – LCS[t]) > DCL)
an intrusion interrupt is sent to the host.
Page 12 of 66
Data Sheet
CC-2401K2 Datasheet Rev 1.5
CC-2401K2