MT312C ZARLINK [Zarlink Semiconductor Inc], MT312C Datasheet - Page 50

• Manufacturer Part Number: MT312C
• Description: Satellite Channel Decoder
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

MT312
M SNR[14:0]: These two registers provide a indication of the signal to noise ratio of the channel being received
by the MT312. It should not be taken as the absolute value of the SNR.
Eb/N0 = ~
The equation given only holds for Es/No values in the range 3 to 15 dB, i.e. Eb/No values in the range 0 to 12
dB.
7.2.4 Viterbi Error Count at Viterbi Input. Registers 11 - 13 (R)
This is effectively the QPSK Bit Error Rate.
VIT ERRCNT[23:0]: This is the count of bits corrected by the Viterbi decoder. This value is updated when the
Viterbi error timer (VIT_ERRPER) expires (indicated by B2 in register FEC_INT) and is NOT reset by reading.
QPSK BER =
7.2.5 Reed Solomon Bit Errors Corrected. Registers 14 - 16 (R)
This is effectively the Viterbi Bit Error Rate.
RS BERCNT[23:0]: These three registers provide a measurement of the number of bit errors corrected by the
Reed Solomon decoder. Reading the high byte stops the count incrementing. Reading the low byte resets all
three bytes and restarts the count incrementing again.
Viterbi BER =
Where: dt = delta time between two readings in sec (recommend 20s for 20 - 30 MBaud signals)
e.g.
Viterbi BER =
50
VIT ERRCNT M
VIT ERRCNT H
VIT ERRCNT L
RS BERCNT M
RS BERCNT H
RS BERCNT L
NAME
NAME
Rs = Symbol rate in Baud
CR = Viterbi code rate
In denominator: the factor 2 is for QPSK, change it to 1 for BPSK
for Rs = 27.5Mbaud, CR = 3/4 and dt = 20 sec
13312 - M SNR[14:0]
------------------------------------------------------- -
RS_BERCNT[23:0] * 4
----------------------------------------------------------- -
------------------------------------------------------------ -
VIT_ERRPER[23:0] * 4
Forward Error Correction
RS_BERCNT[23:0]
-------------------------------------------------- -
20 * 27.5E6 * 2 * 3
VIT_ERRCNT[23:0]
dt * Rs * 2 * CR
683
ADR
ADR
11
12
13
14
15
16
RS BERCNT[7:0] - Reed Solomon bit errors corrected (low byte)
B7
B7
RS BERCNT[23:16] - Reed Solomon bit errors corrected
dB.
RS BERCNT[15:8] - Reed Solomon bit errors corrected
VIT ERRCNT[15:8] - Viterbi error count (middle byte)
VIT ERRCNT[23:16] - Viterbi error count (high byte)
VIT ERRCNT[7:0] - Viterbi error count (low byte)
B6
B6
B5
B5
(middle byte)
(high byte)
B4
B4
B3
B3
B2
B2
B1
B1
B0
B0
R
R
R
R
R
R
Def
hex
Def
hex
00
00
00
00
00
00