Recent changes to longpulses

WikiPage longpulses modified by minstrel

minstrel — Sat, 05 Jan 2013 11:56:25 -0000

--- v4
+++ v5
@@ -25,7 +25,9 @@

 * Long pulses *pl* (pl = cycles) are split up into *n* parts of length 0xffffff; save (n-1) pulses of layout 00 ff ff ff.
 followed by a pulse 00 xx xx xx, with x = pl % 0xffffff.
+* Split the remaining cycles into two long pulses of the same length.

+This ensures that there no artificial "short" pulses are created.

 ###TAP version 2###

@@ -35,3 +37,5 @@
 * for the remaining cycles: 2500 < cycles < 2*0xffffff
 * if (n-1) is even: save 2 pulses with length (remaining cycles / 2)
 * if (n-1) is odd: save 3 pulses with length (remaining cycles / 3)
+
+This ensures that there is always an even number of long "half" pulses, and no artificial "short" pulses are created.

WikiPage longpulses modified by minstrel

minstrel — Sat, 05 Jan 2013 11:42:56 -0000

--- v3
+++ v4
@@ -23,7 +23,8 @@

 This allows for a more precise representation of long pulses:

-* Long pulses *pl* (pl = cycles) are split up into *n* pulses of layout 00 ff ff ff, with n = pl / 0xffffff, followed by a pulse 00 xx xx xx, with x = pl % 0xffffff.
+* Long pulses *pl* (pl = cycles) are split up into *n* parts of length 0xffffff; save (n-1) pulses of layout 00 ff ff ff.
+followed by a pulse 00 xx xx xx, with x = pl % 0xffffff.

 ###TAP version 2###

WikiPage longpulses modified by minstrel

minstrel — Sat, 05 Jan 2013 11:36:06 -0000

--- v2
+++ v3
@@ -29,3 +29,8 @@
 ###TAP version 2###

 For TAP version 2 splitting of pulses into half-pulses needs to be considered.
+
+* n = (cycles / 0xffffff); save (n-1) pulses 00 ff ff ff
+* for the remaining cycles: 2500 < cycles < 2*0xffffff
+* if (n-1) is even: save 2 pulses with length (remaining cycles / 2)
+* if (n-1) is odd: save 3 pulses with length (remaining cycles / 3)

WikiPage longpulses modified by minstrel

minstrel — Fri, 04 Jan 2013 11:38:59 -0000

--- v1
+++ v2
@@ -4,7 +4,7 @@

 According to the original [TAP specification](http://www.computerbrains.com/tapformat.html), long pulses are encoded like this:

-"The data byte value of 00 represents overflow, any pulselength of more than 255*8 cycles."
+The data byte value of 00 represents overflow, any pulselength of more than 255*8 cycles.

 Since this is somewhat underspecified, mtap2 uses the following definition:

@@ -13,3 +13,19 @@
 * Long pulses *pl* (pl = (cycles+7)/8) recorded from the original tape, with pl > 255 are split up into *n* 00 pulses, with n = (pl + 2499) / 2500
 * As a special case, all pulse lengths *pl* with 255 < pl <= 2500 are encoded as exactly one 00 pulse.

+
+###TAP version 1###
+
+According to [TAP spec](http://www.computerbrains.com/tapformat.html), in TAP version 1 long pulses are encoded like this:
+
+Data value of 00 is followed by three bytes, representing a 24 bit value of C64 
+cyles (NOT times 8). The order is as follow: 00   .
+
+This allows for a more precise representation of long pulses:
+
+* Long pulses *pl* (pl = cycles) are split up into *n* pulses of layout 00 ff ff ff, with n = pl / 0xffffff, followed by a pulse 00 xx xx xx, with x = pl % 0xffffff.
+
+
+###TAP version 2###
+
+For TAP version 2 splitting of pulses into half-pulses needs to be considered.

WikiPage longpulses modified by minstrel

minstrel — Fri, 04 Jan 2013 09:59:10 -0000

Handling of long pulses

TAP version 0

According to the original TAP specification, long pulses are encoded like this:

"The data byte value of 00 represents overflow, any pulselength of more than 255*8 cycles."

Since this is somewhat underspecified, mtap2 uses the following definition:

The data byte value of 00 represents a long pulse value of 2500 * 8 cycles.

Long pulses pl (pl = (cycles+7)/8) recorded from the original tape, with pl > 255 are split up into n 00 pulses, with n = (pl + 2499) / 2500
As a special case, all pulse lengths pl with 255 < pl <= 2500 are encoded as exactly one 00 pulse.