AMIS-49587_15 Datasheet, PDF (9/56 Pages) ON Semiconductor – Power Line Carrier Modem

AMIS−49587
TDO, TDI, TCK, TMS, and TRSTB
All these pins are part of the JTAG bus interface. The JTAG interface is used during production test of the IC and will not be
described here. Input pins (TDI, TCK, TMS, and TRSTB) contain internal pull−down resistance. TDO is an output. When not
used, the JTAG interface pins may be left floating.
TX_DATA/PRE_SLOT
TX_DATA/PRE_SLOT is the output for either the transmitting data (TX_DATA) or a synchronization signal with the
time−slots (PRE_SLOT). More information can be found in paragraph Local Port.
XIN
XIN is the analog input pin of the oscillator. It is connected to the interval oscillator inverter gain stage. The clock signal can
be created either internally with the external crystal and two capacitors or by connecting an external clock signal to XIN. For
the internal generation case, the two external capacitors and crystal are placed as shown in Figure 6. For the external clock
connection, the signal is connected to XIN and XOUT is left unused.
XTAL _IN
XTAL_ OUT
R_X
24 MHz
CX
CX
V _SSA
Figure 6. Placement of the Capacitors and Crystal with Clock Signal Generated Internally
The crystal is a classical parallel resonance crystal of 24 MHz. The values of the capacitors C_X are given by the manufacturer
of the crystal. A typical value is 30 pF. The crystal has to fulfill impedance characteristics specified in the AMIS−49587 data
sheet. As an oscillator is sensitive and precise, it is advised to put the crystal as close as possible on the board and to ground
the case.
XOUT
XOUT is the analog output pin of the oscillator. When the clock signal is provided from an external generator, this output must
be floating. When working with a crystal, this pin cannot be used directly as clock output because no additional loading is
allowed on the pin (limited voltage swing).
TXD
TXD is the digital output of the asynchronous serial communication (SCI) unit. Only half−duplex transmission is supported.
It is used to realize the communication between the AMIS−49587 and the application microcontroller. The TXD is an open
drain IO (5 V safe). External pull−up resistances (typically 10 kW) are necessary to generate the 5 V level. See Figure 5 for
the circuit schematic.
RXD
This is the digital input of the asynchronous SCI unit.
Only half−duplex transmission is supported. This pin supports a 5 V level. It is used to realize the communication between the
AMIS−49587 and the application microcontroller. RXD is a 5 V safe input.
T_REQ
T_REQ is the transmission request input of the Serial Communication Interface. When pulled low its initiate a local
communication from the application micro controller to AMIS−49587. T_REQ is a 5 V safe input.
BR1, BR0
BR0 and BR1 are digital input pins. They are used to select the baud rate (bits/second) of the Serial Communication Interface
unit. The rate is defined according to Table 28: BR1, BR0 Baud Rates. The values are taken into account after a reset, hardware
or software. Modification of the baud rate during function is not possible. BR0 and BR1 are 5 V safe.
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