3Jtech uModem Technical Document page 4

HARDWARE DESCRIPTIONS
ZyDAS 56K USB modem solution includes the
modem data pump ZD1051 and Silicon Lab's
Si3034/ Si3035 silicon
provides an optional ROM code ZD10591 to
replace the FEPROM used in this modem. The
hardware function of ZD1051 is described herein.
Please refer to the hardware interface signals of
ZD1051 in Figure 2 for the usage of ZD1051.
ZD1051 Modem Data Pump
The ZD1051 modem data pump consists of a
high performance / low power consumption DSP
core, a high speed data bus for data memory, a
low speed data bus for program memory, a USB
transfer, a serial interface for silicon DAA and a
serial EEPROM interface for modem profiles.
ZD1051 gets the transmit data from the USB
transfer. This data bit stream is converted to an
voice band signal by the ZD1051's DSP core and
sent to the telephone line via the silicon DAA to
the remote modem. The analog waveform on the
telephone line coming from the remote modem is
digitized by the silicon DAA. This digitized signal
is demodulated as received data bit stream by the
DSP core and then transferred to host through
the USB transfer.
The access time of the SRAM connected to the
high speed data bus of ZD1051 must be at least
12 nsec. The access time of FEPROM or ROM
connected to the low speed data bus of ZD1051
should be faster than 120 nsec.
The functions of ZD1051 from the view point of
hardware signals are described as follows.
Power signals (19 pins)
The ZD1051 uses two power supply voltages,
3.3V and 1.8V. 1.8V is used for the operation of
DSP core and logic circuits. 3.3V is used solely
for the I/O pads interfacing to 3.3V peripheral
chips.
VDD33: The 3.3V power source.
●
VDD18: The 1.8V power source.
●
Reset signals (2 pins)
RS#: power on reset input pin. A RC network
●
can be directly connected to the RS# input pin
to generate the desired reset signal when
turning on the system power. (3.3V input, active
low)
RESETO#: This reset output is used to reset
●
peripheral circuits, such as FEPROM and
2003/6 From 3JTech
DAA. ZyDAS also
Revision 1.0
Research & Development
Silicon Lab's DAA circuit. It is active low when
pin RS# is active. (3.3V output, active low)
Clock signals (2 pins)
The clock input frequency is 12 MHz, either an
external clock source or a parallel-mode crystal
circuit can be used as the clock input of ZD1051.
CKSOCI: Crystal oscillator input or the input
●
from an external clock source. (1.8V input)
CKSOCO: Crystal oscillator output. Leave this
●
pin open when an external clock source is
connected to CKSOCI. (1.8V output)
USB interfaces (4 pins)
This interface complies with the USB
specification revision 1.1, supporting 12M bps full
speed and power management requirement.
● DP: USB data signal Data Plus (D+) connects
to USB. (Bi-directional I/O)
● DM: USB data signal Data Minus (D-) connects
to USB. (Bi-directional I/O)
● SUSPEND: This USB suspend output signal is
used to shut off the power of modem when
USB is in suspending state. Connect to the
SHDN input of ZD1056 to save the power. (3.3V
output, active high)
● RPUENO: Use for USB connects or disconnect
control. When reset signal RS# input is low, this
pin is tractate. (3.3V output)
Remote wakeup (1 pin)
When the bus-powered USB modem is in the
suspend state, all the modem circuits, including
ZD1051 and silicon DAA, are powered off except
the always powered circuit in ZD1051. A ring
detection circuit not depending on the switched
power acts as the wakeup signal. This wakeup
signal will be passed to the USB block of ZD151
which will then initiate the resume operation. The
first action of the resume operation is turning off
the SUSPEND output and power will be
resupplied to the modem circuit.
Two ring detection circuits are needed for a USB
bus-powered modem. One must work in the
suspend mode and act to wake up the USB
function. The other ring detection circuit is built-in
in the Si3034/Si3035 silicon DAA. It is the normal
ring detection circuit and can not work in the
suspend mode because power to the
Si3034/Si3035 is shut off.
● RMWK#: Remote wakeup input for wakeup
from USB suspend state. Connect to the output of
an up to ring detector. If the remote wakeup
function is not used, leave this pin open (3.3V
input, active low)
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