AD6654SLASHPCB datasheet(54/88 Pages) AD

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AD6654

Rev. 0 | Page 54 of 88

PCLK

tDPREQ

PxREQ

PxACK

tDPP

Px [15:0]

I[15:0]

Q[15:0]

PxIQ

tDPIQ

PxCH [2:0]

PxCH [2:0] = CHANNEL #

tDPCH

0000 +

GAIN [11:0]

PxGAIN

tDPGAIN

Figure 58. Interleaved I/Q Mode with an AGC Gain Word

PxCH [2:0]

PCLK

tDPREQ

PxREQ

PxACK

tDPP

Px [15:0]

I [15:8]

Q [15:8]

PxIQ

tDPIQ

PxCH [2:0] =

AGC NO.

tDPCH

PxGAIN

LOGIC LOW 0

Figure 59. Parallel I/Q Mode Without an AGC Gain Word

When an output data sample is available for output from an

AGC, the parallel port initiates the transfer by pulling the

PxREQ signal high. In response, the processor receiving the

data needs to pull the PxACK signal high, acknowledging that it

is ready to receive the signal. In Figure 59, the PxACK is already

pulled high and, therefore, the 8-bit I data and 8-bit Q data are

simultaneously output on the data bus on the next PCLK rising

edge after PxREQ is driven logic high. The PxIQ signal also

goes high to indicate that I/Q data is available on the data bus.

When I/Q data is being output, the channel indicator pins

PxCH[2:0] indicate the data source (AGC number).

Figure 59 is the timing diagram for parallel I/Q mode with the

AGC gain word disabled. Figure 60 is a similar timing diagram

with the AGC gain word enabled. In the PCLK cycle after the

I/Q data, the AGC gain word is output on the data bus, and the

PxGAIN signal is pulled high to indicate that the gain word is

available on the parallel port. During this PCLK cycle, the PxIQ

signal is pulled low to indicate that I/Q data is not available on

the data bus. Therefore, in parallel I/Q mode, a minimum of

two PCLK cycles is required to output one sample of output

data on the parallel port without and with the AGC gain word,

respectively.

The order of data output is dependent on when data arrives at

the port, which is a function of total decimation rate, DRCF/

CRCF decimation phase, and start hold-off values. Priority

order from highest to lowest is, AGC0, AGC1, AGC2, AGC3,

AGC4, and AGC5 for both parallel I/Q and interleaved modes

of output.

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