Datasheet

MAX7428/MAX7430/MAX7432A
Standard Definition Video Reconstruction
Filters and Buffers
______________________________________________________________________________________ 11
Applications Information
Maxim’s Single Pin Bus (MSPB)
Serial Interface
The MSPB interface uses three pulses of different
widths to represent commands and data bits. Figure 4
shows the set of pulses that the single pin interface
uses to communicate with the device. A combination of
the one pulse (t
1
), zero pulse (t
0
), transaction pulse (t
T
),
and prompt pulse (t
P
), writes to, reads back from, and
sends broadcast data to the devices on the bus.
Note: The zero pulse and prompt pulse are the same.
Initialization pulses are significantly longer and are
used only on power-up or software reset.
Initializing the
MAX7428/MAX7430/MAX7432A
Initialization is performed only after power-up or software
reset. It assigns a unique address to each device on the
bus. The time constant of the capacitor connected to
R
EXT
in parallel with the 300kΩ resistor determines the
order in which the devices are initialized (address
assigned). The device with the largest time constant is
initialized first and so on, in descending order. Table 7
shows the “Initialize Wait” and “Initialize Time” pulse
widths needed for a specific capacitor value and toler-
ance. Program each device on the bus with this com-
mand sequence starting with the device with the biggest
capacitor. To reinitialize a device, cycle the power or use
a software reset. The following is the command
sequence and timing diagram (Figure 5) for initialization
as shown below. Chip ID is entered LSB first.
Note: If there is only one device on the bus, no initial-
ization is needed. Communicate to the device using the
broadcast command described on page 13.
(MSB)
NAME — ABSEL3
BYPASS3 CLEVEL3 BOOST1(3) BOOST0(3)
OUT
DISABLE3
—
DEFAULT 0 1 1 0 0 0 0 0
NAME — ABSEL2
BYPASS2 CLEVEL2 BOOST1(2) BOOST0(2)
OUT
DISABLE2
—
DEFAULT 0 1 1 0 0 0 0 0
NAME — ABSEL1
BYPASS1 CLEVEL1 BOOST1(1) BOOST0(1)
OUT
DISABLE1
—
DEFAULT 0 1 1 0 0 0 0 0
FIRST BIT
(LSB)
Table 5. MAX7432A Control Register
BOOST1_ BOOST0_
RELATIVE HIGH
FREQUENCY BOOST
00 0
0 1 0.3dB to 0.5dB
1 0 0.6dB to 1.0dB
1 1 0.9dB to 1.5dB
Table 6. Boost Level Programming
ZERO/PROMPT
PULSE
t
P
= t
0
= 5μs
t
1
= 30μs
t
0
ONE PULSE
TRANSACTION
PULSE
t
1
t
T
= 100μs
t
T
Figure 4. MSPB Interface Pulses