Information recording apparatus having parallel to serial and PPM signal converters

A camera comprises a photographic information output circuit section, a CPU, a PPM signal conversion circuit section, a drive section for a plurality of magnetic heads, and a film feeding section. The CPU converts several parallel data items which are output from the photographic information output circuit section into a single serial data item and outputs it to the PPM signal conversion circuit section provided separately from the CPU. The PPM signal conversion circuit section converts this single serial data item into several PPM signals, and then supplies the PPM signals to the magnetic head drive section.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an information recording apparatus which 
magnetically records information which consists of a plurality of bits by 
a PPM recording method. 
2. Related Background Art 
The PPM (pulse position modulation) recording method is a per se known 
method of magnetically recording data upon a magnetic recording medium. 
FIG. 9 is a waveform diagram illustrating this PPM recording method. 
With the PPM recording method, the period of the signal is always kept 
fixed, and the signal levels "0" and "1" are coded by the position of the 
trailing edge of the signal waveform. In concrete terms, if the trailing 
edge of the signal waveform occurs between the start point of the period 
of the signal and its midpoint this is taken as encoding a "0", while if 
the trailing edge of the signal waveform occurs between the midpoint of 
the period of the signal and its end point this is taken as encoding a 
"1". For example, referring to FIG. 9, when the trailing edge of the 
signal waveform occurs at a position approximately one quarter period from 
the head of the signal period this is taken as encoding a "0" (in this 
case, called a PPM signal of 25% bit location), while when the trailing 
edge of the signal waveform occurs at a position approximately three 
quarters period from the head of the signal period this is taken as 
encoding a "1" (in this case, called a PPM signal of 75% bit location). 
The above method enables data to be transmitted correctly even if the 
trailing edge position in the signal period is somewhat shifted due to a 
delay over the data line or other cause. When data of "0" is to be 
transmitted in FIG. 9, it is recognized as data of "0" so long as the 
signal waveform drops before its half period, even if the data that should 
drop at one quarter period from the head of the signal period is lagged to 
actually drop behind the quarter period due to a delay over the data line 
or other cause. As a result, an error in transmission of data is less 
likely to occur. 
Meanwhile, there are known cameras of the type magnetically recording 
photographic information, such as the date and exposure data, on a film, 
and there is also a possibility of taking advantage of the above described 
PPM recording method for such magnetic recording. 
A photographic information output circuit in the camera outputs parallel 
data for information, such as the date and exposure data. Consequently, 
the parallel data has to be converted into serial data first and then the 
serial data has to be converted into a PPM signal in the camera. A 
conventional camera converts the parallel data into the serial data and 
the serial data into the PPM signal by software process of a CPU. 
However, the CPU takes much time to convert all photographic information 
into the PPM signals, because the CPU converts the parallel data which 
indicates the photographic information into the PPM signal one bit by one 
bit. On the other hand, the CPU has to process many functions, such as an 
exposure process and a film feeding process, in addition to the above 
described converting process. Consequently, if the CPU takes comparatively 
long time for the above described converting process, it influences other 
functions. For example, the speed of consecutive shots becomes slow. 
Summary of the Invention 
The object of the present invention is to provide an information recording 
apparatus which converts photographic information into PPM signals without 
using a CPU. 
In order to attain this object, an information recording apparatus 
according to the present invention, which is capable of magnetically 
recording information on a magnetic medium, comprising: an information 
output circuit which outputs parallel data for the information; a clock 
output circuit which outputs a reference clock; a parallel to serial 
conversion circuit which converts the parallel data into serial data based 
on the reference clock; a PPM signal conversion circuit which is provided 
separately from the parallel to serial conversion circuit and converts the 
serial data which is output from the parallel to serial conversion circuit 
into a PPM signal based on the reference clock; and a magnetic recording 
device which magnetically records the converted PPM signal on the magnetic 
medium. 
The information output circuit outputs the parallel data for the 
information, the clock output circuit outputs the reference clock, and the 
parallel to serial conversion circuit converts the parallel data into the 
serial data based on the reference clock and outputs the serial data. The 
PPM signal conversion circuit provided separately from the parallel to 
serial conversion circuit converts the serial data into the PPM signal 
based on the reference clock, and the magnetic recording device 
magnetically records the data of the PPM signal on the magnetic medium. 
With the information recording apparatus according to the present 
invention, converting of the parallel data into the PPM signal can be done 
without using the CPU, whereby the load of the CPU is reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Embodiment 
In the following, a first preferred embodiment of the present invention 
will be described in detail as applied to a camera with reference to FIGS. 
1 through 4. In the block diagram, elements composing a camera which are 
not related to PPM recording are omitted. 
In FIG. 1 the reference numeral 1 denotes a photographic information output 
circuit section which outputs in parallel a plurality of (in the shown 
example, two) data items of photographic information such as, for example, 
the time point of photography and the exposure, and the reference numeral 
2 denotes a CPU which, as shown in FIG. 2, has as input terminals a power 
input terminal Py1 which is connected to a power source 3, a release 
signal input terminal Py2 which is connected to a release switch 4, and 
parallel data input terminals Pz1 through Pzn which are connected to the 
photographic information output circuit section 1. Further, this CPU 2 has 
as output terminals a serial data output terminal SOUT at which it outputs 
serial data, a serial data clock terminal SCK at which it outputs a clock 
signal for synchronizing the serial data output, and a transmission start 
signal terminal Px which provides information for the start of serial data 
transmission. A data line connected to the serial data output terminal 
SOUT is designated in FIG. 1 as L1, while control lines connected to the 
control terminals such as the serial data clock terminal SCK etc. are 
collectively designated as L2. Further, by way of example, it is assumed 
that in the FIG. 1 device two items of parallel data each consisting of 
four bits are output from the photographic information output circuit 
section 1 to the CPU 2. 
The reference numeral 5 denotes a PPM conversion circuit section which 
converts the serial data supplied from the CPU 2 into a PPM signal, the 
detailed structure of which is shown in FIG. 2. As shown in FIG. 2, this 
PPM conversion circuit section 5 comprises D flip-flops D1 through D8, 
inverters INV1 through INV2, AND gates G2, G4, G5, G6, G8 and G9, and OR 
gates G1, G3, G7, and G10. This PPM conversion circuit section 5 separates 
the serial data output from the CPU 2 via its terminal SOUT into two sets 
of serial data PPM1 and PPM2. 
The reference numerals 6 in FIG. 1 denote two magnetic head drive sections 
which control the process of magnetically recording on a film 8 the above 
described two PPM signals which are output from the PPM conversion circuit 
section 5; and 7 denotes a film feeding section which controls the winding 
on of the film 8. 
FIGS. 3 and 4 are flow charts showing the operation of the CPU 2. The 
operation of this first preferred embodiment of the information recording 
apparatus of the present invention will now be explained with reference to 
FIGS. 1 through 4. 
When the power source 3 has been turned on and the release switch 4 has 
been pressed, the CPU 2 starts to execute the program whose flow chart is 
shown in FIG. 3. In this flow chart and in the following explanation, the 
two data items of photographic information (which in this example may be 
the time point of photography and the exposure) output in parallel from 
the photographic information output circuit section 1 will be termed the 
first data item and the second data item; the four bits of which the first 
data item is composed will be termed, in order from the most significant 
bit downwards, d1, d2, d3, and d4; and the four bits of which the second 
data item is composed will be termed, in order from the most significant 
bit downwards, k1, k2, k3, and k4. Further, the number of bits in the 
write memory internal to the CPU 2 used for alternately storing each bit 
of the two parallel data items, and also the number of bits of the serial 
register internal to the CPU 2 used for serially outputting in order one 
bit at a time, will both be assumed to be 8 bits. 
Referring to FIG. 3, in the step S1 normal preparations for photography 
such as measurement of the brightness of the object to be photographed and 
driving of the photographic lens for focusing and the like are performed. 
Next, in the step S2, it is detected whether or not the release switch 4 
has been pressed, and if the release switch 4 has not been pressed the 
flow of control returns to the step Sl, while if the release switch 4 has 
been pressed then the flow of control proceeds to the step S3. In this 
step S3, photographic control operations such as control of lens aperture 
and shutter control are performed. In the next step S4, along with 
instructing film winding to the film feeding section 7 after photography 
has been completed, the value of the number of bits of the data item to be 
transferred is set to zero. In the next step S5 (which is the start of the 
inner program loop from the step S10 to be described hereinafter) the four 
bits contained in the first data item are shifted one bit at a time 
leftwards (in the direction of the most significant bit) and the most 
significant bit is transferred to a bit carry register. Accordingly, in 
this first cycle through the inner program loop, the value of the bit d1 
is transferred to the bit carry register. In the next step S6, the eight 
bits of a write memory are shifted one bit at a time leftwards and the 
contents of the bit carry register are written into the least significant 
bit of the write memory. Accordingly, in this first cycle through the 
inner program loop, the value of the bit d1 is written into this least 
significant bit of the write memory. 
In the next step S7 the four bits contained in the second data item are 
shifted one bit at a time leftwards and the most significant bit is 
transferred to the bit carry register. In the next step S8, the eight bits 
of the write memory are shifted one bit at a time leftwards and the 
contents of the bit carry register are written into the least significant 
bit of the write memory. And in the next step S9 the value of the number 
of bits to be transferred is incremented by one. 
Next, in the decision step S10, a decision is made as to whether or not the 
value of the number of bits to be transferred has become equal to 4. If 
the value of the number of bits to be transferred has not yet become equal 
to 4 then the flow of control returns back to the step S5, and the above 
described process is repeated, so that the first data item and the second 
data item are alternately written one bit at a time into the least 
significant bit of the write memory and the contents of the write memory 
are shifted one bit at a time leftwards. Accordingly, the first data item 
and the second data item are written into the write memory in an 
interleaved manner with their bits being stored in the order 
d1.fwdarw.k1.fwdarw.d2.fwdarw.k2.fwdarw.d3.fwdarw.k3.fwdarw.d4.fwdarw.k4. 
0n the other hand, if in the step S10 it is determined that the value of 
the number of bits to be transferred has become equal to 4, then the flow 
of control proceeds to the step S11, in which as will be described in 
detail hereinafter the contents of the write memory are output from the 
serial data output terminal SOUT. Finally in the step S12 a decision is 
made as to whether or not the film feeding process has been completed, and 
program control waits in a tight loop until the result of this test is 
YES, after which in the step S13 the power source 3 is turned off and 
processing terminates. 
FIG. 4 is a flow chart which shows the details of the above described step 
S11 for performing serial data output. In the first step S100, the 8 bits 
contained in the write memory are transferred to a serial register 
provided within the CPU 2. In the next step S101, the transmission start 
signal terminal Px is raised to high level, thus indicating the start of 
data transmission by the PPM conversion circuit section 5. In the next 
step S102, which forms part of the inner loop of this program section, the 
8 bits of the serial register are output one bit at a time in order from 
the serial data output terminal SOUT, and each time one bit is thus output 
a serial data clock signal is simultaneously output from the serial data 
clock terminal SCK. And next in the decision step S103 a decision is made 
as to whether or not all the serial data has been output, and if serial 
data still remain to be output the flow of control returns back to the 
step S102 again. 
When on the other hand all the serial data has thus been output, the flow 
of control proceeds to the step S104, in which the transmission start 
signal terminal Px is dropped to low level. In the next decision step 
S105, a decision is made as to whether or not the serial data clock signal 
has been output a predetermined number of times, and the system loops back 
to this decision step S105 in a tight loop until the result of this 
decision is YES. When in fact the serial data clock signal has been output 
a predetermined number of times, the flow of control proceeds to the last 
step S106 of this program portion, in which output of the serial data 
clock signal is terminated, and then this program portion ends. 
In this manner, according to this first preferred embodiment, the CPU 2 
outputs both the serial data from the terminal SOUT and the serial data 
clock signal from the terminal SCK which synchronizes with the serial 
data. The serial data clock signal from the terminal SCK is continued to 
be output even after transmission of the serial data from the terminal 
SOUT has been completed, so that all the PPM signals can be created. If 
the output from the serial data clock terminal SCK is stopped in response 
to completion of the transmission of the serial data from the terminal 
SOUT, a part of the PPM signal cannot be created as shown in FIG. 5 
mentioned later. 
FIG. 5 is a timing chart for presenting the timing of certain signals at 
various portions of the PPM conversion circuit section 5 shown in FIG. 2. 
The operation of this PPM conversion circuit section 5 will now be 
explained with reference to FIGS. 2 and 5. 
The serial data clock signal output by the CPU 2 at its SCK terminal is 
inverted by the inverter INV1 and the flip-flop D1 divides the frequency 
of the output of the inverter INV1 by 2. The flip-flop D2 latches the 
serial data output from the terminal SOUT according to the Q output of the 
flip-flop D1, and by doing this the first data item in the serial data 
output from the terminal SOUT is extracted. The Q output of the flip-flop 
D2 is input to the D terminal of the flip-flop D3, and is latched by the 
leading edge of the NQ output of the flip-flop D1. 
On the other hand, the flip-flop D4 latches the serial data output from the 
terminal SOUT according to the NQ output of the flip-flop D1, and by doing 
this the second data item in the serial data output from the terminal SOUT 
is extracted. In this way, the first data item and the second data item 
are extracted with identical timings by the Q outputs of the flip-flops D3 
and D4. 
The flip-flop D5 latches the transmission start signal at the terminal Px 
by the leading edge of the NQ output of the flip-flop D1, and the 
flip-flop D6 latches the Q output of the flip-flop D5 by the leading edge 
of the Q output of the flip-flop D1. The OR gate G1 outputs the logical 
sum of the Q outputs of the flip-flops D5 and D6. This OR gate G1 outputs 
continually high level signal for the period for which the PPM signal is 
output. 
The AND gate G2 outputs the logical product of the serial data clock signal 
at the terminal SCK and the output of the OR gate G1. The flip-flop D7 
divides the frequency of the output of the AND gate G2 by 2 according to 
the leading edge of the output of the AND gate G2. On the other hand, the 
flip-flop D8 divides the frequency of the output of the AND gate G2 by 2 
according to the trailing edge of the output of the AND gate G2. 
The OR gate G3 outputs the logical sum of the Q outputs of the flip-flops 
D7 and D8, and this output of the OR gate G3 becomes the "1" value of the 
PPM signal. The AND gate G4 outputs the logical product of the Q output of 
the flip-flop D7 and the NQ output of the flip-flop D8, and this output of 
the AND gate G4 becomes the "0" value of the PPM signal. The AND gate G5 
outputs the logical product of the Q output of the flip-flop D3 and the 
output of the OR gate G3, and the AND gate G6 outputs the logical product 
of the NQ output of the flip-flop D3 and the output of the AND gate G4. 
The OR gate G7 outputs the logical sum of the output of the AND gate G5 
and the output of the AND gate G6, and by the signal PPM1, which is this 
output of the OR gate G7, the first data item from the photographic 
information output circuit section 1 is converted into the PPM signal and 
is output. 
On the other hand, the AND gate G8 outputs the logical product of the Q 
output of the flip-flop D4 and the output of the OR gate G3, and the AND 
gate G9 outputs the logical product of the NQ output of the flip-flop D4 
and the output of the AND gate G4. The OR gate G10 outputs the logical sum 
of the output of the AND gate G8 and the output of the AND gate G9, and by 
the signal PPM2, which is this output of the OR gate G10, the second data 
item from the photographic information output circuit section 1 is 
converted into the PPM signal and is output. 
The signal PPM 1 which is the output of the above described OR gate G7 and 
the signal PPM 2 which is the output of the above described OR gate G10 
are individually separately supplied to the magnetic head drive section 6 
shown in FIG. 1, and are magnetically recorded on the film 8. 
In this manner, according to the first preferred embodiment, since the CPU 
2 outputs both the serial data and the serial data clock which 
synchronizes with the serial data, it is possible to convert the serial 
data into the PPM signal outside the CPU 2 by using the serial data and 
the serial data clock. Consequently, the CPU 2 does not need to perform 
the process of converting into the PPM signal and can prepare for the next 
photographing immediately after the current photographing is done. As a 
result, the speed of consecutive shots is improved. 
In the above described first preferred embodiment, the system clock of the 
CPU (not shown in Figures) or other clock signals (for example, a divided 
system clock) can be used as the serial data clock from the terminal SCK. 
Second Embodiment 
With the above described first preferred embodiment of the present 
invention, the CPU 2 executes a control program according to the flow 
chart shown in FIG. 3 for converting into serial data the parallel data 
which has been output from the photographic information output circuit 
section 1, but it is also possible to realize these functions in hardware 
rather than in software. The second preferred embodiment of the present 
invention, now to be described, is of this type; and the circuitry in this 
case is shown in FIG. 6, which corresponds to FIG. 2 for the first 
preferred embodiment. 
Referring to FIG. 6, the reference numeral 10 denotes a parallel to serial 
conversion circuit section, the details of the construction of which are 
shown in FIG. 7. As shown in that figure, this parallel to serial 
conversion circuit section 10 comprises serial registers PS1 and PS2, a 
flip-flop D11, AND gates G11 and G12, an OR gate G13, and a counter CNT1. 
Further, FIG. 8 is a timing chart showing the operation of this parallel 
to serial conversion circuit section 10. 
The parallel data which has been output from the photographic information 
output circuit section 1 is input to the input terminals Pz1 through Pzn 
of this parallel to serial conversion circuit section 10. And also a 
system clock signal CLOCK which has been output from the CPU 2 is input to 
a clock terminal CLOCK of the parallel to serial conversion circuit 
section 10. And, based upon this clock signal, the parallel to serial 
conversion circuit section 10 outputs the serial data output signal from 
its terminal SOUT and the serial data clock signal from its terminal SCK, 
and inputs them to the PPM conversion circuit section 5. 
Referring to FIG. 7, the flip-flop D11 divides the frequency of the clock 
signal CLOCK from the CPU 2 by 2. The Q output of this flip-flop D11 is 
input to the clock terminal of the shift register PS1. Further, the first 
data item which has been output from the photographic information output 
circuit section 1 is supplied to the data terminals of this shift register 
PS1, and this first data item is converted into serial data and is output 
from the output terminal of this shift register PS1. 
Similarly, the NQ output of this flip-flop D11 is input to the clock 
terminal of the shift register PS2. Further, the second data item which 
has been output from the photographic information output circuit section 1 
is supplied to the data terminals of this shift register PS2, and this 
second data item is converted into serial data and is output from the 
output terminal of this shift register PS2. 
As shown in FIG. 8, the outputs of these shift registers PS1 and PS2 have a 
period of two pulses of the system clock signal CLOCK. An AND gate G11 
outputs the logical product of the Q output of the flip-flop D11 and the 
output of the shift register PS1, while an AND gate G12 outputs the 
logical product of the NQ output of the flip-flop D11 and the output of 
the shift register PS2. Referring again to FIG. 8, these AND gates G11 and 
G12 output the first data item and the second data item, respectively, 
with the lengths of those bits thereof which are equal approximately with 
the length of a period of the system clock signal CLOCK. An OR gate G13 
outputs the logical sum of the output of the AND gate G11 and the output 
of the AND gate G12, and thus this output of the OR gate G13 consists of 
the first data item and the second data item in alternatingly interleaved 
form, as shown in FIG. 8. CNT1 is a counter, and when a reset signal is 
input to its reset terminal RS the counter CNT1 brings the transmission 
start signal which is output from the terminal Px to low level, while when 
this reset is released the counter CNT1 counts the number of pulses of the 
system clock signal CLOCK. While this count is continuing, the 
transmission start signal which is output from the terminal Px is 
maintained at high level, and when a predetermined number of clock pulses 
have been counted again the counter CNT1 brings the transmission start 
signal which is output from the terminal Px to low level. As shown in FIG. 
8, this transmission start signal is thus maintained at high level during 
just that time interval in which serial data is being output from the 
serial data output terminal SOUT. 
In this manner, according to this second preferred embodiment, since the 
process of converting the parallel data which is output from the 
photographic information output circuit section 1 into the serial data is 
also performed outside the CPU 2, the load of the CPU 2 is reduced much 
more. 
Now, although for the purposes of example in the above described first and 
second preferred embodiments of the present invention two items of 
parallel data were combined and were converted into a single serial data 
item, this is not to be considered to limit the present invention: it 
would also be possible, according to the principles of the present 
invention, to combine three or more items of parallel data and to convert 
them into a single serial data item. Further, the number of bits in each 
of the parallel data items is not to be considered as being limited to 
four. Yet further, the present invention is capable of application, 
regardless the nature of the plurality of parallel data items which are 
input to the CPU 2. Also, although the information recording apparatus of 
the present invention has been described in terms of the above described 
first and second preferred embodiments which relate to its particular 
application to a camera, in fact the present invention can be applied very 
widely to various other devices as well, other than a camera, such as for 
example to a tape recorder or a cassette streamer or the like. 
Accordingly, although the present invention has been shown and described 
in terms of several preferred embodiments thereof, it is not to be 
considered as being limited by any of the perhaps quite fortuitous details 
of the embodiments or of the drawings, but only by the terms of the 
appended claims, which follow.