MT312 MPEG Packet Data Output
9.4 Data output timing
Q*R*P PLL
The number of PLL clocks per Byte clock is: N = ----------------- * ---------- truncated to an integer
2*V RS
Where: Q = 1 for QPSK, 2 for BPSK
R = 204/193 for DVB, 147/135 for DSS
P = 8 for parallel byte output, 1 for serial byte output
V = Viterbi code rate, i.e. 3/4 for ASTRA
PLL = Sampling frequency MHz
RS = Symbol rate in MBaud, i.e. 27.5MBaud for ASTRA
e.g. For DVB ASTRA
N
N
= 1 * 204/193 * 8/2 * 4/3 *90E6/27.5E6
= 18
The transport Stream clock rate = PLL / N
= 90E6 / 18
= 5E6Hz
The time to transmit a packet
= 204 * 8/2 * 4/3 *1/RS
= 1088 / RS
= 3.9564E-5 sec
Time to output 188 bytes
The gap between packets
= 188/5E6
= 3.76E-5 sec
= 3.9564E-5 - 3.76E-5
= 1.936E-6 sec
The gap as number of byte clocks = 1.936E-6 * 5E6
= 9.82
t
CLKP
MCLKIV=1
MOCLK
t
CLKL
t
OD
MOSTRT
MOVAL
MDO7:0
BKERR
Figure 25 - MT312 output data wave form diagram 2
Parameter
Symbol
Min
Typ
Max
Units
Data output delay (when MCLKINV = 1)
tOD
±2
±4
ns
58
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