MT312 Datasheet, PDF (30/90 Pages) Zarlink Semiconductor Inc – Satellite Channel Decoder

MT312 DiSEqC Control
5.2 DiSEqC Control Read/Write Registers
5.2.1 DiSEqC™ Mode Control. Register 22 (R/W)
NAME
ADR
B7
B6
DISEQC MODE 22 Reserved HV
B5
B4
B3
DISEQC
instruction length
B2 B1 B0
22kHz mode
Def
hex
R/W 00
B7: Reserved.
Must be set low.
B6: HV H/V polarisation control: High = Horizontal, DISEQC[1] pin = high
Low = Vertical, DISEQC[1] pin = low
The DISEQC[1] pin controls the externally generated 13/18V LNB voltage.
B5-3: Number of bytes in DiSEqC™ instruction minus 1, to output on DISEQC[0] pin.
i.e. if the message contains four bytes, program B5-3 with the value three.
B2-0:
DiSEqC™ mode:
0:
22kHz off
1:
22kHz on continuous
2:
Burst mode - on for 12.5ms = '0'
3:
Burst mode - modulated 1:2 for 12.5ms = '1'
4:
Modulated with bytes from DISEQC INSTR
5-7:
Reserved.
Note:
for modes 2 and 3, an interrupt is generated 16ms after the '0' or '1' burst.
for mode 4, there is a 16ms delay before the message bytes, then an interrupt is generated 16ms after
the last message byte has been sent. The requisite number of bytes must be pre-loaded into
DISEQC INSTR (register 36) before this bit is set, see 31.
5.2.2 DiSEqC(tm) Ratio. Register 35 (R/W)
NAME
ADR
B7
DISEQC RATIO 35
B6
B5
B4
B3 B2 B1 B0
Def
hex
DISEQC RATIO[7:0]
R/W 00
DISEQC RATIO[7:0] This must be programmed to set the Diseqc output tone frequency.
F_out =
F_xtal
4*DISEQC_RATIO[7:0]
Where F_out is in kHz and F_xtal is in MHz.
For a 22kHz output tone, DISEQC RATIO[7:0] = 11.364 * F_xtal
e.g. with F_xtal = 10MHz, DISEQC RATIO[7:0] = 114, or for 15 MHz 170.
30