Rohde & Schwarz SMIQ02B - External Serial Modulation Data

Digital Modulation SMIQ
1125.5555.03 E-92.96
2.10.5.1 External Serial Modulation Data
Serial modulation data can be fed bit-by-bit via connector DATA. For modulation types with more than
1 bit/symbol, the MSB is applied first (MSB first). Either an external bit clock or symbol clock or the
internal clock can be used. The symbol clock serves as strobe to mark the LSB of a symbol. If an
external bit clock is applied, the data at the active clock edges have to be in a stable state. With external
symbol clock, the bit clock for reading the data is internally generated in the modulation coder (internal
data clock). The following figures show the timing at the interface. In all the cases shown, the active
clock edge is assumed to be positive.
DATA (input)
BIT CLOCK (input)
Fig. 2-54 External serial data and bit clock
Data change should take place only on the negative clock edge.
DATA (input)
SYMBOL CLOCK (input)
Internal dataclock
LSBMSB
Fig. 2-55 External serial data and symbol clock, 3 bit/symbol
SYMBOL CLOCK = High marks the LSB. A status change of DATA and SYMBOL CLOCK
should be performed synchronously.
BIT CLOCK (output)
SYMBOL CLOCK (output)
DATA (input)
Internal dataclock
LSB
MSB
Fig. 2-56 External serial data, internal clock signals
External serial modulation data is selected in the menu by SOURCE-SOURCE-EXT_SER.