PAVLODA (Penetrator version)
----------------------------
Info by Fabrizio Gennari (fabrizio.ge@tiscalinet.it)
Can be found on Penetrator (actually, Penetrator has one short block in old Pavloda format,
the rest uses this loader)
Endianess: MSbF
Theoretically, there are 6 types of pulses
Type Threshold (clock cycles) TAP byte
---------------------------------------------------
very short 0xf2 (242)
short 0x1a6 (422) $2c
medium 0x258 (600) $41
long 0x358 (856) $57
very long 0x50c (1292)
extremely long
Each pulse is shorter than its threshold, and longer than the previous one's threshold.
Actually, only 3 pulse types, Short, Medium and Long, are used.
---------------------------------
Encoding...
Pulses have a different meaning, depending on the current "Status" :
When in Status 1...
---------------------------------
Pulse | Bit pattern | New Status
---------------------------------
Short | 1 | 1
Medium | 00 | 2
Long | 01 | 1
---------------------------------
When in Status 2...
---------------------------------
Pulse | Bit pattern | New Status
---------------------------------
Short | 0 | 2
Medium | 1 | 1
Long | 1 | 1
---------------------------------
Initial status = 2.
-----------------------------
Structure
----------------------
At the start, there is a repeated pattern of pulses like:
MMSSSSS
(M=medium, S=short)
If initial status is 1, it decodes to 00111111, and the final status is 1
If initial status is 2, it decodes to 10000000, and the final status is 2
When looking for sinchronization, if the byte $3F (00111111) is encountered,
status is forced to 2. This causes the synchronization to the right status, before
synchronizing on the right bit.
Lead-in byte : $08 (00001000) (no less than 255 of them, typically 1280)
Sync byte : $55
2 bytes : Start address (low,high)
2 bytes : End address (low,high)
n bytes : Data (n = End address - Start address)
1 byte : Checksum (sum of all n data bytes + n) & 0xFF.
In other words you need to add all n Data bytes and add 1 for each of them.
(
geocities.com/siliconvalley/platform/8224) (
geocities.com/siliconvalley/platform) (
geocities.com/siliconvalley)