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CXD1217M

Description of Operation (See Block Diagram.)

The CXD1217 is applicable to four systems; namely, NTSC, PAL, PALM and SECAM. In order to realize them,

the following relative equations of Sub-carrier (4fsclN) and Clock (CLIN) are adopted .

As it is obvious from the above equations, the 4fsc and clock frequency do not coincide with each other in the

PAL and PALM. Therefore matching of the clock frequency is carried out by providing PLL.

1 . MODE specified input

The CXD1217 provides four inputs to specify the respective modes.

∗ EXT input: Set this pin to V

DD

side, and it becomes into external synchronizing mode. At this time, the

counters in connection with the PLL Ioop as shown in the upper part of the block diagram

become into stand still state.

∗ MODE1 and MODE2 inputs: These are inputs for the system selection.

∗ TEST input: An input to be used to measure IC. This input is normally kept opened.

(Because it is dropped internally to Vss with MOS resistance.)

2. Reset operation

The CXD1217 has three reset inputs ; namely, HRI, VRI, LALTRI, and it works to perform reset operation

when it detects falling edge. These three inputs are so designed as to take in synchronization with the IC

internal clock. Therefore, it is a prerequisite that both systems should have clock frequencies that are matched

as a reset operation to each other (GEN Iocked).

• H reset (HRI input)

When the HRI input is continuous with H synchronization, resetting is activated with the initial falling edge,

and for the subsequent edges they do not have to be reset unless they are deviated more than 2-bit (140ns)

against the initial edge in the internal clock. That is, if the jitter of HRI input is less than 140ns, it is absorbed.

The minimum resetting pulse width is over 0.3µs.

The phase to be reset is the advanced point of 6.3 to 6.37µs (= 90 to 91-bit

× 70ns) than the HRI input as

shown in the diagram below.

Reset

6.3 to 6.37 [µs]

HRI input

CXD1217

HD OUT output

NTSC

PAL

PALM

SECAM

—

Sub carrier

Clock

MODE1

0

0

1

1

MODE2

0

1

0

1

System

NTSC

SECAM

PALM

PAL

"0"

"1"