diff --git a/doc/img/zio-block.png b/doc/img/zio-block.png
new file mode 100644
index 0000000000000000000000000000000000000000..f2b6bd06ec239ec75470d487ca41cbb982bf1e86
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diff --git a/doc/img/zio-block.ps b/doc/img/zio-block.ps
new file mode 100644
index 0000000000000000000000000000000000000000..53d157d3c4a8750da2635dfa4636c00859a41736
--- /dev/null
+++ b/doc/img/zio-block.ps
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+%%Creator: Alessandro Rubini
+%%Title: crap
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+%%EndComments
+
+0 0 moveto
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+ stringwidth pop div dup 3 1 roll % scale string scale
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+ currentfont exch scalefont setfont % scale string
+ show
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+ 3 1 roll moveto
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+/rect { % x y wid hei --
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+ wid neg 0 rlineto closepath
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+} def
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+/redforrect {.5 .2 .2 1 .8 .8} def
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+/Helvetica-Bold findfont 7 scalefont setfont
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+% righe di controllo
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+60 140 moveto 10 0 rlineto 20 20 rlineto 10 0 rlineto stroke
+60 130 moveto 80 0 rlineto stroke
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+140 130 moveto -6 1.5 rlineto 0 -3 rlineto closepath fill
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+ 45 140 (Block) centeratsize
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+greforrect 100 140 30 30 colrect
+ 115 160 (Control) centeratsize
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diff --git a/doc/img/zio-control.png b/doc/img/zio-control.png
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diff --git a/doc/img/zio-control.ps b/doc/img/zio-control.ps
new file mode 100644
index 0000000000000000000000000000000000000000..957f4aad5ea153500ce5c25bcfe0e4be936584ed
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+++ b/doc/img/zio-control.ps
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+%!PS-Adobe-2.0 EPSF-1.2
+%%Creator: Alessandro Rubini
+%%Title: crap
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+43 260 moveto
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+() line
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+(uint8_t more_ctrl; /* number of further ctrl, for interleaved */) line
+(uint8_t alarms; /* set by channel, persistent, write 1 to clr */) line
+() line
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+(uint32_t nsamples; /* number of samples in this data block */) line
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+(uint16_t chan_i; /* index of channel within cset */) line
+() line
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+(uint8_t hostid[8]; /* Macaddress or whatever unique */) line
+() line
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+(struct zio_timestamp tstamp;) line
+() line
+(/* byte 56 */) line
+(uint32_t mem_offset; /* position in mmap buffer of this block */) line
+(uint32_t reserved; /* possibly another offset, or space for 64b */) line
+() line
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+(/* The control block includes what device the data belongs to */) line
+(char devname[ZIO_OBJ_NAME_LEN];) line
+() line
+(/* byte 76 */) line
+(/* Each data block is associated with a trigger and its features */) line
+(char triggername[ZIO_OBJ_NAME_LEN];) line
+() line
+(/* byte 88 */) line
+(struct zio_ctrl_attr attr_channel;) line
+(struct zio_ctrl_attr attr_trigger;) line
+() line
+(/* byte 488 */) line
+(uint8_t __fill_end[ZIO_CONTROL_SIZE - 488];) line
+
+showpage