M37274MA Datasheet, PDF (41/131 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER

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MITSUBISHI MICROCOMPUTERS
M37274MA-XXXSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
(9) Data clock generating circuit
This circuit generates a data clock synchronized with the start
bit detected in the start bit detecting circuit.
Set the time from detection of the start bit to occurrence of the data
clock in bits 3 to 7 of clock run-in detect register 2 (address
00E916). The time to be set is represented by the following expression:
Time = (13 + set value) ! reference clock period
For a data clock, 16 pulses are generated. When just 16 pulses have
been generated, bit 7 of the data slicer control register is set to “1”
(refer to Figure 26). When method 1 is already selected as a start bit
detecting method, this bit becomes a logical product (AND) value
with a clock run-in determination result by setting bit 7 of the start bit
position register to “1.”
When method 2 is already selected as a start bit detecting method
and 16 pulses are generated of a data clock regardless of bit 7 of the
start bit position register, this bit is set to “1.” The contents of this bit
are reset at a falling of the vertical synchronizing signal (Vsep).
Table 5. Setting Conditions for Caption Data Latch Completion Flag
Bit 7 of SP
Conditions for Setting Bit 7 of DSC1 to “1”
Conditions for Setting Bit 4 of DSC3 to “1”
0
Data clock of 16 pulses has occured in main data slaice line Data clock of 16 pulses has occured in sub-data slaice line
1
Data clock of 16 pulses has occured in main data slaice line Data clock of 16 pulses has occured in sub-data slaice line
AND
AND
Clock run-in pulse are detected 4 to 6 times
Clock run-in pulse are detected 4 to 6 times
(10) 16-bit Shift Register
The caption data converted into a digital value by the comparator is
stored into the 16-bit shift register in synchronization with the data
clock. For the main data slice line, the contents of the high-order 8
bits of the stored caption data and the contents of the low-order 8
bits of the same data can be obtained by reading out data register 2
(address 00E516) and data register 1 (address 00E416), respectively.
For the sub-data slice line, the contents of the high-order 8 bits and
the contents of the low-order 8 bits can be obtained by reading out
the data register 4 (address 00ED16) and data register 3 (address
00EC16), respectively. These registers are reset to “0” at a falling of
Vsep. Read out data registers 1 and 2 after the occurence of a data
slicer interrupt (refer to (11) Interrupt Request Generating Circuit).
(11) Interrupt Request Generating Circuit
The interrupt requests as shown in Table 6 are generated by
combination of the following bits; bits 5 and 6 of the clock run-in register
3 (address 020916), bit 1 of the clock run-in register 2 (address
00E716). Read out the contents of data registers 1 to 4 and the
contents of bits 3 to 7 of clock run-in detect registers 1 and 3 after the
occurence of a data slicer interrupt request.
Table 6. Occurence Sources of Interrupt Request
CR3
b5
b6
0
0
1
0
CR2
b1
0
1
0
1
0
1
Occurence Souces of Interrupt Request
Slice line
At end of data slice line
Sources
Main data slice line
Data clock of 16 pulses has occured
AND
Clock run-in pulse are detected 4 to 6 times
Data clock of 16 pulses has occured
At end of data slice line
1
0
1
1
Sub-data slice line
Data clock of 16 pulses has occured
AND
Clock run-in pulse are detected 4 to 6 times
Data clock of 16 pulses has occured
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