Cermetek Microelectronics, Inc.
CH1787 Small Footprint Hardware Controllable 2400bps Modem
Parameter
Table 4. CH1787 System Data Mode Compatibility Specifications.
Specification
Parameter
Specification
Asynchronous
2400, 1200, 600bps character Receive Carrier Originate+HZ 2400Hz +7Hz
asynchronous.
0-300bps Frequencies Answer
1200Hz +7Hz
asynchronous
V.22bis, V.22, 212A
Asynchronous
Speed Range
TxD may differ +1%, -25% from
modem output. Offsets will be
corrected by adding/deleting stop
bits.
Bell 103
Answer ‘space’ 2025Hz +7Hz
Answer ‘mark’ 2225Hz +7Hz
Originate ‘space’ 1070Hz +7Hz
Originate ‘mark’ 1370Hz +7Hz
Asynchronous 8, 9, 10bits, including start, stop, Receiver Sensitivity OFF to ON threshold -43 dam
Format
parity
On to OFF threshold -48 dam
Telephone Line
Interface
Two-wire full duplex over public
switched network. On-chip hybrid
and billing delay timers.
Modulation
V.22bis, 16 point QAM at
600baud. V.22 and 2212A, 4
point, DPSK at 600baud. 103
binary phase coherent FSK.
Hysteresis
2dB minimum
Self Test Pattern
Generator
Alternate ‘ones’ and ‘zeros’ and
error detector, to be used along
with most loopbacks. A number
indicating the bit errors detected
is sent to DTE.
Line Equalization
Fixed compromise equalization,
transmit. Adaptive equalizer for
PSK/QAM, receive.
Transmit Carrier
Frequencies
V.22bis, V.22,
212A
Originate 1200Hz +.01%
Answer 2400Hz +.01%
Diagnostics
Available
Local analog loopback.
Local digital loopback.
Request remote digital loopback.
Local interface loopback modem
with self-test.
Bell 103 mode
Originate ‘space’ 1070Hz +.01%
Originate ‘mark’ 1270Hz +.01%
Answer ‘space’ 2025Hz +.01%
Answer ‘mark’ 2225Hz +.01%
Call Progress Tones With speaker or quiet screen
Detected
messages (no dial tone, busy,
ring-back, modem answer tone
and voice).
Computer Interface IBM PX/XT/AT bus compatible
with an 8250/16450/16550A
UART as a serial controller.
2002 Cermetek Microelectronics, Inc.
Page 12
Document No. 607-0002 Revision B (03/02)