s MSM7712 s –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

12

Oki Semiconductor

MODEM Interface

The MSM7712 provides FH PLPC framing and the FH modem as defined by the IEEE 802.11 specifica-

tion.The radio synthesizer control pins are used for all modem options. A diagnostic port is provided

when the internal modem is used. Several options are provided by the internal FH modem selected by

the PHY_VER[MSEL] register bits. The following table shows the pin usage for various modem options.

1.

All modem signals are synchronized to RCK.

Modem Interface

FH Mbps (Low Cost)

FH 1/2 Mbps (Normal ADC)

FH 1/2 Mbps (Delta ADC)

MSEL

1

2

3

IFD[]

IFD[5:0] to TXIF DAC

IFD[4] carries SLICE on RX

IFD[5:0] to TXIF

DAC and IFD[3:0] from RXADC

IFD[5:0] to TXIF DAC (also used for Delta ADC)

RXD

Baseband RX data from radio

Recovered data (Debug out)

Input from Delta ADC comparator

Modem Interface Signal Descriptions

Pin Name

Direction

Description

IFD[5:0]

Bidirectional

If MSEL=1 (low cost for 1Mbps modem), IFD[5:0] are used to drive a 6-bit DAC at 32 MHz to provide the mod-

ulated transmit IF signal at 24 MHz. They are set to the DAC mid-value during receive. It is anticipated that a

resistor ladder DAC will be used.

If MSEL=2,3, (1/2 Mbps modem), IFD[5:0] are used to drive a 6-bit DAC at 32 MHz to provide the modulated

transmit IF signal at 24 MHz.

If MSEL=2 (1/2 Mbps modem, normal ADC) a 4-bit ADC (e.g. CA3304 type) provides digitized demodulated

data at 16 MHz as input to the baseband controller on pins IFD[3:0] during receive. The ADC outputs must

only be enabled during receive (e.g. by connecting RXC1 to the ADC output enable pin).

If MSEL=3 (1/2 Mbps modem, delta ADC), a comparator is used to compare the value of the transmit IF DAC

output to the receive demodulated signal, performing a tracing delta ADC function. The same 6-bit DAC (but

at 16 MHz) is used on IFD[5:0] as during transmit, and the comparator input is connected to the RXD pin

RIFD[5:0]

Bidirectional

With MSEL=2 (1/2 Mbps modem, normal ADC) a 4-bit ADC (e.g. CA 3304 type) provides digitized demodu-

lated data at 16 MHz as input to the baseband controller on pins IFD (3:0) during receive. The ADC outputs

must only be enabled during receive (e.g. by connecting RXC) to the ADC output enable pin.

RXD

Input

When MSEL=1 (low-cost 1 Mbps modem), the RXD pin is used for baseband data input from a radio which

has a built-in analog data slicer. The MSM7712 has a clock recovery circuitry to synchronize to the incoming

data. The recovered clock is output on a diagnostic pin for test purposes.

When MSEL=3 (1/2 Mbps modem, delta ADC), the delta comparator is input on this pin. The recovered clock

from the demodulator is output on a diagnostic pin for test purposes.

DIAG[6:0]

Output

Various signals are provided on these pins as diagnostic aids. The registers PHY_CTL[DIAG] and

DEM_CTL0[DTST] select what signals are provided on these pins.