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Cypress Semiconductor Corporation • 3901 North First Street • San Jose • CA 95134 • 408-943-2600
April 1994 – Revi sed June 23
,
1998
Innovative RoboClock™ Family Application
Introduction
This application note presents a unique application of the
RoboClock™, using its complex and precise waveform gen-
eration capability to implement PWM (Pulse Width Modula-
tion) to enhance color images and increase the resolution of
laser printers. The first section of this application note pro-
vides a brief description of RoboClock and presents three
methods that the user can employ to configure it. Second, a
brief background on image and resolution enhancement is
presented. Finally, the required waveform to implement the
image enhancement and the configuration of RoboClock is
presented.
Overview of RoboClock
The CY7B991 and CY7B992, commonly known as
RoboClock, are pr ogramm abl e skew clock bu ffers ca pable of
generating thousands of various clocking combinations. As
shown in
Figure 1
, the eight high drive outputs are arranged
in four pairs, which can be configured by three-level inputs
(HIGH, LOW, and MID logic level). The internal PLL is fully
self -contained and does not require a ny ext ernal components
to operat e. The PLL bu ffer stages are dif ferential, greatl y en-
hancing t he robust ness of t he PLL operation in t erms of jitt er
over vol tage, and tempe ratur e vari ati ons.
Basically, the PLL aligns the output clock i n both phase and
frequency with the reference clock. The simplest mode of
operati on is the low- skew out put mode. In this mode the out -
puts are vi rtually skewless. The m aximum skew is on ly a f ew
hundred picoseconds. Please refer to the CY7B991/992
datasheet for various skew specifi cations. The sec ond m ode
is the programmable skew mode. The outputs of RoboClock
can be ske wed (adv anced and dela yed) by increm ents of one
time un it (tU) , which is 0.7 t o 1.5 ns, det ermined by the oper-
ating frequency and range of the PLL.
t
U
= 1/(F
nom
* N) Eq. 1
As show n in
Table 1
, the frequency r ange of the PLL is det er-
mined by the three-level FS input . For ea ch fr equency ra nge,
there is a correspon din g integer “N” that can be used in
Equa-
tion 1
to calculate tU. Up to ±12tU skew can be achieved
between t he out put s of Rob oCloc k (positi v e t U repr esents de-
laying the output with respect to REF and negative tU repre-
sents advanci ng the outpu t with respect to REF).
The th ird m ode of operat ion i s the Mul ti- funct ion m ode. I n thi s
mode the out puts may be mult iplied by 2 or 4, divided by 2 or
4, or inverted. Most importantly, the skew features can be
combined with multiply, divide, and inver t functions. This re-
sults in, literally, over 26,000 timing configurations. For more
detailed information on the operation of the RoboClock,
please refer to the following application notes “Using the
CY7B991 with the 50-MHz 486 Cache Module and the
40-MHz R3000” and “Everything You Need to Know About
CY7B991/2 (RoboClock) and the RoboClock Family”. This
appli cation note is mean t to comp lemen t the topi cs discus sed
in above mentioned application notes.
Usuall y , on e of the output s of RoboCloc k is used as t he Feed-
back i nput. If the desired waveform is not directly generated
by RoboCl ock, an imagi nativ e user may run an out put of Rob-
oCloc k through a logic bl ock, the n send i t back to th e FB input
of the RoboCl ock. Through thi s scheme, unl imited additional
functions may be implemented by RoboClock. Note that in
this case, all the other outputs of the RoboClock will be shifted
by a period equal t o the dela y thr ough the ex ternal logic bloc k,
because the PLL will align the FB input with the REF input,
both in phase and f requency.
Figure 1. Logic Block Diagram
TEST
FB
REF
VCO AND
TIME UNIT
GENERATOR
FS
SELECT INPUTS
(THREE LEVEL) SKEW
SELECT
MATRIX
4F0
4F1
3F0
3F1
2F0
2F1
1F0
1F1
4Q0
4Q1
3Q0
3Q1
2Q0
2Q1
1Q0
1Q1
FILTER
PHASE
FREQ
DET
Table 1. Frequency Range Select and tU Calculation
FS
fNOM (MHz)
where N =
Approximate
Frequency
(MHz) At Which
tU = 1.0 nsMin. Max.
LOW 15 30 44 22.7
MID 25 50 26 38.5
HIGH 40 80 16 62.5
tU1
fNOM N×
------------------------=
Innovative RoboClock Family Application
2
Cascading two RoboClocks in series will also dramatically
increase the output possibilities. In this case, one of the out-
puts of the fir st stag e wil l serve as the REF input for the sec-
ond stage. Multiple feedback configurations are possible,
which can result in an innovative set of outputs.
RoboClock Configuration Methodologies
Using One Small Table
The entire set of programmable skew configurations is sum-
marized in a single small table shown in
Tabl e 2
. Every pos-
sibl e combination can be driven from thi s sm all tabl e. For ex-
ample, if +2tU is required from 3Qx (3Q0 or 3Q1) outputs,
based on
Table 2
, th e correspondi ng 3Fx input s should be set
as 3F1= MID and 3F0=HIGH. Any one of 1Qx, 2Qx, or 4Qx
outputs may be used as FB input, by leaving its corresponding
1Fx, 2Fx, or 4Fx inputs floating (i.e., 1F1= MID, 1F0= MID).
Note that
Table 2
represents only the cases where the feed-
back is an output with no skew, divide, or invert function. Ba-
si ca lly, a 0tU output is used for FB input.
Now, to generate additional output functions, if the feedback
output is programmed to skew, divide or invert, then output
func tions of other o utp uts m ay n ot b e dire ctly rea d from
Table
2
. In this ca se , to figur e out the final output f uncti on obs erv ed
on the output, simply subtract whatever the feedback term is
programmed to, from t he outp ut func ti on progr amm ed on th e
corresponding output. Therefore, by using only
Table 2
and
the following simple algorithm, every single combination of
RoboClock can be figured out .
Final Output Function = O utput Function – FB Function
If t here is any am bigui ty, the following example should cl arify
the use of this method. Let’s say +7tU of delay is required.
Ob vious ly, +7tU is not a choice , av ai lab le in
Table 2
. Ho wever ,
any two functions from two different outputs of
Tab l e 2
may
be com bined t o achi eve a desired fu nction . For this ex am ple,
there are several sol uti ons, and only one of them wil l be pre-
sented. One way to achieve +7tU is to subtract –3tU from +4tU.
+7t
U
= +4t
U
– (–3t
U
)
Therefore, if 1Qx out put i s progr am med to have –3t U of skew
(1F1=LOW, 1F0=MID), and used as the FB input, and if the
3Qx is programmed to have +4tU of skew (3F1=HIGH,
3F0=LOW), the final output f unction observ ed on 3Qx wil l be
+7tU.
One exception to this simple rule is that if a divided output is
used as the FB inpu t, the n the othe r output s will be m ult iplied
by t he sa me f acto r (2 or 4). Th e r eason f o r thi s is t hat th e PLL
will force the FB to align with the REF both in phase and
frequency. Therefore , if the FB term is programm ed to di vide
by 2, the PLL wil l speed up t wic e to f orce t he FB term to ali gn
with the REF frequency . As an example, if advance by 6tU and
multi ply by 4 function is requi red (–6tU and f*4) , then
Final Function = –6t
U
– (divi de by 4) => (– 6t
U
and f*4)
The solution for this example is to program 3Qx to divide by
4 (3F1=HIGH, 3F0=HIGH) and use it as FB, and program 4Qx
to hav e – 6tU of skew (4F1=LOW , 4F0=MID). The final function
observed on 4Qx will be REF frequency multiplied by 4 and
advanced by 6tU (−6tU and f*4).
By this metho d, one can easi ly d ete rmine if a de sired func tion
can be implemented by RoboClock or not. RoboClock can
generate a wav eform composed of any two functions from two
different outputs of
Table 2
.
Using Three Tables for Multiple Outputs
If multiple outputs with var ious functions are required, using
the previous method could be a little cumbersome. All the
possible combinations of RoboClock outputs are in three ta-
bles , i llu s tra ted in
Tabl es 3
through
5
. Each table represents
all th e possib le outpu t combinat ions with a given output co n-
nected to FB input. For example, once 3Qx output is used as
FB input, then all the possible output combinations could be
found in
Tab l e 4
. These three tables are extremely valuable
tools in dete rmining wh at FB term to u se and how to confi gure
the RoboClock, when mul tiple outputs with var ious functions
are required.
Once the req uired m ult iple funct i ons are det ermi ned in te rms
of tU, an effort shou ld be m ade to l ocate one r ow in one o f the
three tables that contains the required functions. For exam-
ple, if one of t he de sired funct ions i s divid e by 2 an d dela y 4tU
(+4tU an d f/2), t hen by observation, that c hoice can be l ocated
in row 1 of
Table 3
, row 3 of
Table 4
, and row 3 of
Table 5
.
Now, the one to be selected as a solution would depend on
what the other required functions are, because once an out-
put, which is programmed to perform a certain function, is
selected as FB input, all the outputs of a RoboClock are lim-
ited to a single row found in
Tables 3
through
5
. If in the pre-
vious example, the second required function happens to be
invert and skew b y 4tU (+4tU and INV), then the only solution
is ro w 1 of
Table 3
. In this case 1Qx could b e used as the FB
input with its inputs hardwired to GND (1F1=LOW,
1F0=LOW), and 3F1=HIGH, 3F0=HIGH to generate (+4tU
and f/2) function on 3Qx outputs, and set 4F1=HIGH,
4F0=HIGH to generate (+4tu and INV) function on 4Qx out-
puts. In this configuration, the 2Qx outputs could be pro-
grammed to have any one of 0tU through +8tU sk ew. For ex-
ample, if +7tU is another required output, then 2F1=High,
2F0=Mid will generate +7tU skew on 2Qx. Note that even
though the 1Qx outputs are programmed to have –4tU skew,
they a re forced by PL L to al ign wi th t he REF fr equency, t here-
fore 1Qx out put coul d be used as a 0tU output.
The Table method is recommended for multiple outputs with
various function requirements. If the exact required outputs
cannot al l be f ound i n one row, then the designe r can use the
Table 2. Output Adjustment Configurations
Function Selects Output Functi ons
1F1, 2F1,
3F1, 4F1 1F0, 2F0,
3F0, 4F0 1Q0, 1Q1,
2Q0, 2Q1 3Q0, 3Q 1 4Q0, 4Q 1
LOW LOW –4tUDivide by 2 Divide by 2
LOW MID –3tU–6tU–6tU
LOW HIGH –2tU–4tU–4tU
MID LOW –1tU–2tU–2tU
MID MID 0tU0tU0tU
MID HIGH +1tU+2tU+2tU
HIGH LOW +2tU+4tU+4tU
HIGH MID +3tU+6tU+6tU
HIGH HIGH +4tUDivide by 4 Inverted
Innovative RoboClock Family Application
3
three tables to understand the design choices that are avail-
able within the three tables. Based on the design require-
ments , the user can mak e a judgement on wh at outpu ts m ust
exactly meet the required specs, and what outputs may be
sli ghtl y compromised. If the required outputs are not found in
one r o w of t he three tabl es , an d no compr omise can be mad e
on the requirements, then two or more RoboClocks may be
used to meet the spe cific required output s.
Using RoboClock in Resolution
Enhancement of a Laser Printer
Background
Laser printers are no different from any other electrical sys-
tems, in that the higher the resolution or the accuracy of the
system, the higher the complexity and cost of the system. It
has been and will always be the goal of system and design
engineer s to achi eve th e highest perf ormance and r esolut ion
at the lo w est cost
In t he case of a lase r print er, to a chiev e higher resolutio n than
the nomin al low-end 300 DPI (dot per inch), the throug hput of
the processor, size of the memory, and the glue logic should
incr eas e accord ingly. I n many cas es , the a ddi tional ha rdw are
cost doe s no t ju stify t he enhan cement i n the r esolut ion. A f e w
year s ago, a new technique called Resolution Enhancement
Technology (RET) was developed by Hewlett Packard. The
main advantage of this technique versus conventional reso-
lution enhancement techniques is that the resolution en-
hancem ent is ga ined with har dl y any in crease i n th e throug h-
put of the processor or memory size. Therefore, this approach
is a very econ om ical way of gaining enhanced re solut ion.
F or obvi ous reasons, the ent ire l aser pri nter industry is using
some f orm of th is techni que. V a rious fla v ors of the same tech-
nique are bei ng ap plied to diff er ent imag e-enhanc ement ma-
chines. The halftones or gray scales are common in most
laser printers. The underlying technique is fairly simple. This
is accomplished by modulating the laser beam, as opposed
to the conventi onal “on” or “off” stat e of the la ser beam, f or the
entir e cycle time . The laser beam could be turned “on” or “o ff”
25%, 50%, 75% or 100% of the period. By this, large and
small dots c an be pr oduced on a giv en i mage , th eref ore g ai n-
ing much hi gher “perceived” resolution compared with imag-
es constructed by only one size dot. The varying size dots
produce much smoother text files and generate much sharper
images through shades of gray. Refer to
Figur e 2
a and
2b
.
The same idea is used in color image enhancement where
much smoother an d more pl easant image s may be p rodu ced
in a gi ven col or i mage b y d ilatin g b lac k do ts and s hrinki ng the
red. This filtering or color enhancement feature can be used
to produce various special effects, or simply be employed to
create more appealing color images. Please refer to
Figure
3a
and
Figure 3b
To further clarify this technique, the true
resolution, technically, stil l remains t he same , but the i ma ges
are “pe rceive d” to be hi gher resol ution. It does n ot matter how
the “better image” was created, as long as it looks good and
the cost of t he hardware is affordable.
.
.
Figure 2. Laser Images
Figure 3. Color Enhancem ents
a. Standard un modu lat ed b. Modulated l aser beam with s horter “on”
periods and variable-size dots.
a. Black dot dilated b. Re d dot shrunk
Innovative RoboClock Family Application
4
Design Implement ation
RoboClock is used to generate precise complex waveforms
needed for laser beam modulation. The par ticular laser sys-
tem discussed in th is appl ication not e requi res eigh t l evels of
modulation, which consists of 100% on, 75% on, 50% on,
25% on, 100% off, 75% off, 50% off, and 25% off. The eight
w aveforms are shown in
Figure 4
.
Note that all waveforms are synchronized t o the rising edge
of the system clock.Analyzing the entire circuitry of the laser
printer is beyond the scope of this application not e, and only
the waveform modulation section is discussed. The system
clock runs at 66.67 MHz, which translates into 15 ns cycle
time. The simplified diagram of the modulation section is
shown in
Figure 5
. The modu la tion s ection cons ists of a Rob-
oClock, a 256K*4 SRAM that contains the pixel information,
four NOR gates with complemented outputs, and an 8:1
MUX. In this application, since the laser head interface uses
ECL levels, 500 ps ECL NOR gate with complemented out-
puts (MC10E101) and ECL 8:1 MUX (MC10E163) is used.
Unused inputs of the quad four input NOR gates are tied
LOW. The TTL outputs of CY7B991 are translated into ECL
levels by Cypress Semiconduct or high-speed, low-skew TTL
to E CL t ransl ator (CY10 E384L). To k ee p the mod ul ation logic
diagram simple, the translate block is not shown in
Figure 5
.
Note that, general ly, 74AS logic parts are used to impl em ent
external logic functions, which requires no translate logic to
interface with RoboClock.
The 66.67-MHz system clock is fed to the REF input of the
RoboClock. RoboClock generates very precise waveforms
and, wi th one l e v el of gati ng, al l t he six mod ul ated wa v e fo rms
are produced and fed to the 8:1 MUX. For this design, Rob-
oClock generates precise 90-degree phase-shifted, true and
complemented versions of the 66.67-MHz REF input frequen-
cy. Note that only six waveforms are generated. The “100%
on” and “100% off” modes ar e hardwired HIGH and LOW to
the 8:1 MUX. Thre e bit s of t he SRAM are used to sel ect one
out of eight possible modulated signals. The output of very
fa st MUX is direct ly sent to the la ser head. There fore , all eigh t
le v els of modulated wa v ef orms are presen t at the i nput of the
MUX at all times. Only one is routed to the laser head, de-
pending on the requi red modulat ion le vel st ored in th e SRAM.
Generally, one should be ver y cautious about using t he out-
put of a MUX, since during the period when MUX select bits
are changing, the MUX output will usually be glitching, until
the MUX s elect b its ar e stabi liz ed. Thi s beha vi or is due to the
fact that all the select bits do not arrive at exactly the same
time . Even i f the y di d arrive at the sa me time, dela y pat h vari -
ation s and l ogi c s wi tchi ng int ernal t o MUX ma y cre ate a gli tch
on the output. As a word of caution, the above mentioned
scheme should not be used for a clocking scheme. When a
new MUX inpu t is selected, ther e wil l probably be a glitch on
the output. If the first cycle gli tch can be tol erated or masked,
then t his scheme can be used fo r clock distributio n. A dela yed
clocked version of the MUX output could be safely used for
Figure 4. Generated Waveforms
REF (66.67 MHz)
F
F
+4tU
100% HIGH
75% HIGH
50% HIGH
25% HIGH
100% LO W
75% LOW
50% LOW
25% LOW
tp = 15 ns
Innovative RoboClock Family Application
5
clock distribution. Obviously, the delay should be larger than
the maximum propagation delay of MUX. For this particular
application, the glitch is not as important, because the total
duration of ON and OFF times of the laser beam is the con-
cern, not the risin g or f al ling edges of t he w av eform. Als o, th e
laser head is turned off during the MUX address selection,
totally masking any possible glitches.
Configuring RoboClock and Design Analysis
A close observation of waveforms shown in
Fi g u r e 5
reveal s
the fundamental idea behind generating all six modulated
waveforms. Simply by gating the 90-degree phase-shifted
REF with the true and complemented version of the REF
cloc k , all s ix wav e fo rms are generat ed. F or simpli cit y’ s sake ,
lets call the 90-degree phase-shifted waveform +4tU,
66.67 -MHz c loc k F, and t he in v erted clo c k F. Let’s look at ho w
each one is gener ated.
75% HIGH: (+4tU) OR (F)
50% HIGH: F
25% HIGH: (+4tU) NOR ( F)
75% LOW: (+4tU) NOR (F)
50% LOW: F
25% LOW: (+4tU) OR (F)
Note that very fast NOR gates with true and complemented
outpu ts were sel ected to achiev e unif orm dela y for all outp uts.
Also, the 50% HIGH and 50% LOW signals are routed OR
gates configu red as buf f ers to ensure matc hed dela y si gnals .
Please note that all three RoboClock outputs, +4tU, F, and F,
have the same number of loads. It is very important during
layout to match all the trace l engths from RoboCloc k to NOR
gates and from the NOR gates to the MUX to prevent unde-
sirable skew, which will translate into phase shift and pul se-
width variation on the laser beam.
Ov er voltage and t em perat ure variation, all the outp uts of the
RoboClock ar e very st able . The PLL in side th e RoboClock is
construc ted f rom diff er ent ial stages , whi ch mak es i t se lf-c om-
pensating against voltage and temperature variations. Con-
sequently, RoboClock generates robust output waveforms in
terms of phase and frequency. The external OR gates may
disto rt the w a veform due to t he ef f ects of voltage an d temper -
ature variatio n.
Earlier, the 90–degree phase-shifted waveform was equated
with +4tU. Let ’s see how that was derived. Ba sed on
Table 1
,
each time uni t is calculat ed by the following equation:
t
U
= 1/(F
nom
* N) Eq. 2
Where, as indicated in the
Table 1
, N can be any one of 44,
26, or 16 integer numbers, depending on the maximum output
frequency of the RoboClock. Since the output frequency is
66.67 MH z, the n FS is sel ected t o be HIG H (freq uency ra nge
of 40 to 80 MHz), N = 16, and Fnom = 66.67 MHz. By simply
plugging the numbers in the
Equation 2
, the tim e unit or th e
tU can be calculated as:
t
U
= 1/(66.67 MHZ * 16)
t
U
= 0.9375 ns
Figure 5. Simplif ied Laser Modulation Diagra m
66.67 MHz
VCC
FB
REF
FS
4F0
4F1
3F0
3F1
2F0
2F1
1F0
1F1
TEST
4Q0
4Q1
3Q0
3Q1
2Q1
2Q0
1Q1
1Q0
LOW
F
+4tU
F
LOW
100% HIGH HIGH
75% HIGH
50% HIGH
25% HIGH
100% LOW LOW
75% LOW
50% LOW
25% LOW
A0
A1
A2
A3
A4
A5
A6
A7
QA
QA
S2 S1 S0
MUX SELECT
BITS FROM SRAM
TO LASER
HEAD
GND
GND
CY7B991 8:1
MUX
Innovative RoboClock Family Application
6
In terms of phase shift, if 66.67 MHz or 15-ns cycle time is
360 de gr ees , t hen the 90- degree pha se-shi ft i s esse nti all y 15
ns di vided by 4.
90 Degr ee Phase Shift = 15 ns / 4 = 3.75 ns
Therefore, the number of time units to shift to obtain 90-de-
gree phase-shift, is simply derived by dividing 3.75 ns by tU.
Number of Time Units = 3.75 ns / 0.9375 = 4
Therefore , in FS = HI GH mode , 4 t U t rans lates into 90- degre e
phase-shi ft. An observant reader might ha ve already notice d
the fact that in FS = HIGH mode, N is equal to 16, based on
Table 1
. Thi s me ans that , in FS = HIGH mode , an e ntir e cy cle
or 360 degrees, is equivalent to the delay through 16 stages
of ring oscillator, and each stage represents one tU (In FS =
LO W the number of delay stages or N is 44 and in FS = MI D
it is 26. As shown in
Figure 6
note that the actual number of
ring oscilla tor b uffe r stag es is hal f t he N, b ecause each cycle
contain s a LOW and HIGH perio d, whi ch means to complet e
a full cycle the signal propagates through the ring oscillator
twice.) In order to derive a 90-degree phase-shift, all one
needs to do is to m ult iply N b y 1/4 ( wher e 90/360 = 1 /4 cyc le).
Therefore, 16/4 = 4 time units, in FS = HIGH mode, repre-
sents a 90 degree phas e shift .
The same simple methodology can be used to figure out the
number of time units of delay or advance to implement a n
arbitrary degree of phase shift. The number of units of skew
(TU needed for an arbitrary phase shift is calculated as fol-
lows:
Eq. 3
Rounding this number to the nearest integer will introduce a
small phase error fro m the desir ed phase shift. F or exampl e,
if 60 degr ee phase shi ft is required when FS = LOW, then:
Required Phase Shi ft = 60/36 0 = 1/6 cycl e
Number of Time Uni ts = N * 1/6 = 44/6 = 7.33 t
U
Since the number of PLL stages for each FS mode is an in-
teger n umber , then the nearest time unit shift, in this case , will
be seven. Obviousl y, thi s wil l create a phase error of 0. 33 tU.
,
#T
U
N phaseshift
–
360
----------------------------------------=
Figure 6. Distributed-Phase Clock Oscillator and Output Adjust Matrix
Vcon
FS –6 –4 –3 –2 –1 0 +1 +2 +3 +4 +6 /2 /4
1F0
Distributed-Phase Taps Divided & Inverted Taps
1F1
2F0
2F1
3F0
3F1
4F0
4F1
1Q0
1Q1
2Q0
2Q1
3Q0
3Q1
4Q0
4Q1
Innovative RoboClock Family Application
7
Let’s go back and discuss how the +4tU, F and F wavefo rms
are generated by RoboClock. Since multiple outputs from a
single RoboClock is expected, as an exercise, let’s use the
three-table method. There are several solutions for the cur-
rent requirement; only one of the simplest is presented. By
observing
Table 3
, titled as “1Qx/2Qx Output Connected to
FB Input,” one may select the 1Q0 to be used as FB, and
leave the corresponding inputs floating (1F0=1F1=MID).
Thus, essentially, we have access to all the terms available
in r o w two of the gi v en ta b le. Now, b y sel ecti ng the i npu ts, the
RoboClock may be configured to generate various wave-
f orms. By sett in g 2F0=2F1=MID or f lo ating the 2F x inputs , th e
2Q0 and 2Q1 will generate the required F signal (also, 1Qx
could have been used for F signal). Setting 3F0=LOW and
3F1=HIGH wil l gener ate +4t U signal at 3Q0 and 3Q1. Finall y,
setting 4F0=4F1=HIGH will generate the F signal. As men-
ti oned earli er , b y fixing th e f ee dback t erm, in thi s case , all th e
elements of the 2nd row of
Table 3
are avai labl e for the user.
RoboClock is a flexible clock distribution buffer that may be
reconfi gured easily during the pr otot yping phase of a desi gn.
For e xam ple, if instea d of gener atin g a 0 TU output o n 2Q x, i t
is re quired to ha ve the 2Qx sign als advanc ed by 2tU, then t his
can be accomplished simply by setting 2F0=HIGH and
2F1=LOW. This is one of the commonly used features of
RoboClock t hat of fers thousands of variati ons for prototypin g
purposes. Often, during prototyping phase, some modifica-
tion i n the cl ock or the wa vef orm is required.
RoboClock, with its thousands of configurations, resolves
some of the unexpecte d timi ng probl em s. In fact, during pr o-
totyping, if multiple timing variations are expected, it is ad-
vised to use a three-st ate regi ster to driv e the RoboCloc k in-
puts. Then, each output of the register must have a 10K
pull-up and 10K pull-down resistor, to ensure that MID level
is held at half the supply voltage when the register is
three-stated. In this case, the user may write a word in the
input register, and by doing so, reconfigure the entire opera-
tion of the RoboClock, without using any jumpers. Note that
not all the inpu ts need to be recon figurab le fo r a given des ign.
Often, a couple of reconfigurable signals ar e all that is need-
ed. In that case, most inputs ma y be hardwired and the i nputs
needed to re configure v arious output s ma y be register ed with
the 10K pull-up and pull-down resistors.
Summary
RoboClock was used to generate very precise complex
wav e f orms to enh ance c olor im ages and i ncrease the resol u-
tion of laser printers. Even though RoboClock is widely used
for clock distribution, this applicati on note present ed an alter-
native use of RoboClock for complex precise waveform gen-
eration.
Table 3. 1Qx or 2Qx Output Connec ted to FB Input (Part 1)
Feedback Section 2Qx Output Section
1Qx(2Qx)→FB
Configuration
Block
2Qx(1Q x) Output s with respect to REF
2F1
(1F1) L L L M M M H H H
1F1
(2F1) 1F0
(2F0) 2F0
(1F0) L M H L M H L M H
LL
Output Sel ecti on
Block
0t +1t +2t +3t +4t +5t +6t +7t +8t
L M –1t 0t +1t +2t +3t +4t +5t +6t +7t
L H –2t –1t 0t +1t +2t +3t +4t +5t +6t
M L –3t –2t –1t 0t +1t +2t +3t +4t +5t
M M –4t –3t –2t –1t 0t +1t +2t +3t +4t
M H –5t –4t –3t –2t –1t 0t +1t +2t +3t
H L –6t –5t –4t –3t –2t –1t 0t +1t +2t
H M –7t –6t –5t –4t –3t –2t –1t 0t +1t
H H –8t –7t –6t –5t –4t –3t –2t –1t 0t
Innovative RoboClock Family Application
8
Table 3. 1Qx or 2Qx Output Connec ted to FB Input (Part 2)
Feedback Section 3Qx Output Section
1Qx(2Qx)→FB
Configuration
Block
3Qx Outputs with respect to REF
3F1 L L L M M M H H H
1F1
(2F1) 1F0
(2F0) 3F0 L M H L M H L M H
LL
Output Selection
Block
+4t,
f/2 –2t 0t +2t +4t +6t + 8t +10t +4t, f/4
LM +3t,
f/2 –3t –1t +1t +3t +5t +7t +9t +3t,f/4
LH +2t,
f/2 –4t –2t 0t +2t +4t +6t +8t +2t,f/4
ML +1t,
f/2 –5t –3t –1t +1t +3t +5t +7t +1t,f/4
MM 0t,
f/2 –6t –4t –2t 0t +2t +4t +6t 0t,f/4
MH –1t,
f/2 –7t –5t –3t –1t +1t +3t +5t –1t,f/4
HL –2t,
f/2 –8t –6t –4t –2t 0t +2t +4t –2t,f/4
HM –3t,
f/2 –9t –7t –5t –3t –1t +1t +3t –3t,f/4
HH –4t,
f/2 –10t –8t –6t –4t –2t 0t +2t –4t,f/4
Table 3. 1Qx or 2Qx Output Connec ted to FB Input (Part 3)
Feedback Section 4Qx Output Section
1Qx(2Qx)→FB
Configuration
Block
4Qx Outputs with respect to REF
4F1 L L L M M M H H H
1F1
(2F1) 1F0
(2F0) 4F0 L M H L M H L M H
LL
Output Selection
Block
+4t,
f/2 −2t 0t +2t +4t +6t +8t +10t +4t
INV
LM +3t,
f/2 −3t −1t +1t +3t +5t +7t +9t +3t
INV
LH +2t,
f/2 −4t −2t 0t +2t +4t +6t +8t +2t
INV
ML +1t,
f/2 −5t −3t −1t +1t +3t +5t +7t +1t
INV
MM 0t,
f/2 −6t −4t −2t 0t +2t +4t +6t 0t
INV
MH −1t,
f/2 −7t −5t −3t −1t +1t +3t +5t −1t
INV
HL −2t,
f/2 −8t −6t −4t −2t 0t +2t +4t −2t
INV
HM −3t,
f/2 −9t −7t −5t −3t −1t +1t +3t −3t
INV
HH −4t,
f/2 −10t −8t −6t −4t −2t 0t +2t −4t
INV
Innovative RoboClock Family Application
9
Table 4. 3Qx Output Connected to FB Input (Part 1)
Feedback Section 1Qx, 2Qx Ou tput Sectio n
3Qx→FB
Configuration
Block
1Qx (2Qx) Out puts with respect to REF
1F1
(2F1) L L L M M M H H H
3F1 3F0 1F0,
(2F0) L M H L M H L M H
LL
Output Sel ection
Block
−4t,
f*2 −3t
f*2 −2t
f*2 −1t
f*2 0t
f*2 +1t
f*2 +2t
f*2 +3t
f*2 +4t
f*2
L M +2t +3t +4t +5t +6t +7t +8t +9t +10t
L H 0t +1t +2t +3t +4t +5t +6t +7t +8t
ML −2t −1t 0t +1t +2t +3t +4t +5t +6t
MM −4t −3t −2t −1t 0t +1t +2t +3t +4t
MH −6t −5t −4t −3t −2t −1t 0t +1t +2t
HL −8t −7t −6t −5t −4t −3t −2t −1t 0t
HM −10t −9t −8t −7t −6t −5t −4t −3t −2t
HH −4t
f*4 −3t
f*4 −2t
f*4 −1t
f*4 0t
f*4 +1t
f*4 +2t
f*4 +3t
f*4 +4t
f*4
Table 4. 3Qx Output Connected to FB Input (Part 2)
Feedback Section 3Qx Output Section
3Qx→FB
Configuration
Block
4Qx Outputs with respect to REF
4F1 L L L M M M H H H
3F1 3F0 4F0 L M H L M H L M H
LL
Output Sele cti on
Block
0t –6t,
f*2 –4t,
f*2 –2t,
f*2 0t
f*2 +2t,
f*2 +4t,
f*2 +6t,
f*2 INV,
f*2
LM +6t,
f/2 0t +2t +4t +6t +8t +10t +12t +6t,
INV
LH +4t,
f/2 −2t 0t +2t +4t +6t +8t +10t +4t,
INV
ML +2t,
f/2 −4t −2t 0t +2t +4t +6t +8t +2t,
INV
MM 0t,
f/2 −6t −4t −2t 0t +2t +4t +6t 0t,
INV
MH −2t,
f/2 −8t −6t −4t −2t 0t +2t +4t −2t,
INV
HL −4t,
f/2 −10t −8t −6t −4t −2t 0t +2t −4t,
INV
HM −6t,
f/2 −12t −10t −8t −6t −4t −2t 0t −6t,
INV
HH 0t,
f*2 –6t,
f*4 –4t,
f*4 –2t,
f*4 0t,
f*4 +2t,
f*4 +4t,
f*4 +6t,
f*4 INV,
f*4
Innovative RoboClock Family Application
© Cypress Semiconductor Corporation, 1998. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use
of any circui try other than circuitry embodied in a Cypress Semic onductor product. Nor does it conv ey or imply any license under patent or other rights . Cypress Semi conductor does not authorize
its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress
Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
RoboClock is a trademark of Cypress Semiconduct or Corporation.
Table 5. 4Qx Output Connected to FB Input (Part 1)
Feedback Section 1Qx, 2Qx Ou tput Section
4Qx→FB
Configuration
Block
1Qx, 2Qx Out puts with respect to REF
1F1,
2F1 L L L M M M H H H
4F1 4F0 1F0,
2F0 L M H L M H L M H
LL
Output Selection
Block
–4t,
f*2 –3t,
f*2 –2t,
f*2 –1t,
f*2 0t,
f*2 +1t,
f*2 +2t,
f*2 +3t,
f*2 +4t,
f*2
L M +2t +3t +4t +5t +6t +7t +8t +9t +10t
L H 0t +1t +2t +3t +4t +5t +6t +7t +8t
M L –2t –1t 0t +1t +2t +3t +4t +5t +6t
M M –4t –3t –2t –1t 0t +1t +2t +3t +4t
M H –6t –5t –4t –3t –2t –1t 0t +1t +2t
H L –8t –7t –6t –5t –4t –3t –2t –1t 0t
H M –10t –9t –8t –7t –6t –5t –4t –3t –2t
H H –4t,
INV –3t,
INV –2t,
INV –1t,
INV 0t,
INV +1t,
INV +2t,
INV +3t,
INV +4t,
INV
Table 5. 4Qx Output Connected to FB Input (Part 2)
Feedback Section 1Qx, 2Qx Ou tput Sectio n
4Qx→FB
Configuration
Block
4Qx Outputs with respect to REF
3F1 L L L M M M H H H
4F1 4F0 3F0 L M H L M H L M H
LL
Output Selection
Block
0t –6t,
f*2 –4t,
f*2 –2t,
f*2 0t
f*2 +2t,
f*2 +4t,
f*2 +6t,
f*2 0t,
f/2
LM +6t,
f/2 0t +2t +4t +6t +8t +10t +12t +6t,
f/4
LH +4t,
f/2 –2t 0t +2t +4t +6t +8t +10t +4t,
f/4
ML +2t,
f/2 –4t –2t 0t +2t +4t +6t +8t +2t,
f/4
MM 0t,
f/2 –6t –4t –2t 0t +2t +4t +6t 0t,
f/4
M H –2t,
f/2 –8t –6t –4t –2t 0t +2t +4t –2t,
f/4
H L –4t,
f/2 –10t –8t –6t –4t –2t 0t +2t –4t,
f/4
H M –6t,
f/2 –12t –10t –8t –6t –4t –2t 0t –6t,
f/4
HH INV,
f/2 –6t,
INV –4t,
INV –2t,
INV 0t,
INV +2t,
INV +4t,
INV +6t,
INV INV,
f/4
