LM1882CM National Semiconductor, LM1882CM Datasheet - Page 5
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LM1882CM
Manufacturer Part Number
LM1882CM
Description
IC PROGRAM VIDEO SYNC GEN SO20
Manufacturer
National Semiconductor
Type
Video Syncr
Datasheet
1.LM1882CM.pdf
(16 pages)
Specifications of LM1882CM
Applications
Monitors, TV
Mounting Type
Surface Mount
Package / Case
*
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
*LM1882CM
Signal Specification
HORIZONTAL AND VERTICAL GATING SIGNALS
Horizontal Drive and Vertical Drive outputs can be utilized as
general purpose Gating Signals. Horizontal and Vertical Gat-
ing Signals are available for use when Composite Sync and
Blank signals are selected and the value of Bit 2 of the Sta-
tus Register is 0. The Vertical Gating signal will change in the
same manner as that specified for the Vertical Blank.
Horizontal Gating Signal Width = [REG(16) − REG(15)] x
Vertical Gating Signal Width:
CURSOR POSITION AND VERTICAL INTERRUPT
The Cursor Position and Vertical Interrupt signal are avail-
able when Composite Sync and Blank signals are selected
and Bit 2 of the Status Register is set to the value of 1. The
Cursor Position generates a single pulse of n clocks wide
during every line that the cursor is specified. The signals are
generated by logically ORing (ANDing) the active LOW
(HIGH) signals specified by the registers used for generating
Horizontal and Vertical Gating signals. The Vertical Interrupt
signal generates a pulse during the vertical interval speci-
fied. The Vertical Interrupt signal will change in the same
manner as that specified for the Vertical Blanking signal.
Horizontal Cursor Width = [REG(16) − REG(15)] x ckper
Vertical Cursor Width = [REG(18) − REG(17)] x hper
Vertical Interrupt Width = [REG(14) − REG(13)] x hper
= [REG(18) − REG(17)] x
FIGURE 3. Equalization/Serration Interval Programming
(Continued)
ckper
hper
FIGURE 2. Vertical Waveform Specification
5
Addressing Logic
The register addressing logic is composed of two blocks of
logic. The first is the address register and counter (AD-
DRCNTR), and the second is the address decode (AD-
DRDEC).
ADDRCNTR LOGIC
Addresses for the data registers can be generated by one of
two methods. Manual addressing requires that each byte of
each register that needs to be loaded needs to be ad-
dressed. To load both bytes of all 19 registers would require
a total of 57 load cycles (19 address and 38 data cycles).
Auto Addressing requires that only the initial register value
be specified. The Auto Load sequence would require only 39
load cycles to completely program all registers (1 address
and 38 data cycles). In the auto load sequence the low order
byte of the data register will be written first followed by the
high order byte on the next load cycle. At the time the High
Byte is written the address counter is incremented by 1. The
counter has been implemented to loop on the initial value
loaded into the address register. For example: If a value of 0
was written into the address register then the counter would
count from 0 to 18 before resetting back to 0. If a value of 15
was written into the address register then the counter would
count from 15 to 18 before looping back to 15. If a value
greater than or equal to 18 is placed into the address register
the counter will continuously loop on this value. Auto ad-
dressing is initiated on the falling edge of LOAD when AD-
DRDATA is 0 and LHBYTE is 1. Incrementing and loading of
data registers will not commence until the falling edge of
LOAD after ADDRDATA goes to 1. The next rising edge of
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