MT312 Zarlink Semiconductor, MT312 Datasheet - Page 34

• Manufacturer Part Number: MT312
• Description: Satellite Channel Decoder
• Manufacturer: Zarlink Semiconductor

6.2.2
DISEQC_RATIO[7:0] must be programmed to set the DiSEqC
For a 22kHz output tone, DISEQC_RATIO[7:0] = 11.364 * F
or for 15 MHz 170.
For this example, the DISEQC frequency
For a 10MHz crystal, the tone frequency range is from 9.8kHz with DISEQC_RATIO = 255 to 250kHz with
DISEQC_RATIO = 10. A lower value than 10 causes the tone frequency to become unstable, until the DISEQC
RATIO = 0, the default, value giving a 22kHz tone frequency. This range is not guaranteed, the maximum tone
frequency should be used with caution.
6.2.3
Up to eight instruction data bytes are first loaded into a bank of registers through this register. The 2-wire automatic
register address incrementing is turned off during this loading by setting bit-7: IAI = 1 in RADD, (register address).
The number of bytes (less one) must be defined in the DiSEqC™ instruction register DISEQC_MODE[5:3].
When the DiSEqC
program DISEQC_MODE[5:3] as required. The instruction data bytes are modulated onto the 22kHz signal and
output from the DISEQC[0] pin.
An interrupt is generated 16ms after all the data bytes have been sent and the MT312 then resets
DISEQC_MODE[5:0] to zero, see Figure 18 - “A DiSEqC™ data byte interrupting a continuous 22kHz tone,” on
page 32.
DISEQC_RATIO
DISEQC_INSTR
NAME
NAME
DISEQC ratio register 35 (R/W)
DISEQC instruction register 36 (R/W)
i.e. DISEQC_MODE[5:3] = (number of bytes in the DiSEqC™ instruction) - 1
™
ADR
ADR
35
36
instruction data bytes have been loaded, set DISEQC_MODE[2:0] = 4. At the same time
F
Where F
out
=
bit-7
bit-7
4*DISEQC_RATIO[7:0]
out
is in kHz and F
bit-6
bit-6
F
xtal
=
bit-5
bit-5
------------------ -
4
Zarlink Semiconductor Inc.
10
DISEQC_RATIO[7:0]
DISEQC_INSTR[7:0]
114
xtal
7
bit-4
bit-4
MT312
is in MHz
=
34
21.93kHz
xtal
bit-3
bit-3
™
e.g. with F
output tone frequency.
bit-2
bit-2
xtal
bit-1
bit-1
= 10MHz, DISEQC_RATIO[7:0] = 114,
bit-0
bit-0
R/W
R/W
Design Manual
Def hex
Def hex
00
00