Brother International HL-1070 Technical Reference - Page 103

Offset count = 2 Replacement count = 4 Replacement data = 66 76543 210 11 1 0 0 0 0 1 Optional offset count byte = 0 Replacement data = 11 2001/10/02 Replacement count = 1 + 2 = 3 Offset count = 3 76543 210 11 0 0 0 0 1 0 Replacement data = 66 Replacement count = 2 + 2 = 4 Offset count = 2 • # = 1152 indicates that CCITT G3/G4 data compression is to be used. This format is popular in optical document storage areas as this compression is effective to store black and white type pictures. As G3/G4 format does not have picture size/resolution information, the printer requires a header at the beginning of the picture data. The header size is 94 Bytes. Both the header and the picture data are transferred by the ESC*b###W(###=data length) command. The normal PCL transfer graphics data command has a limitation on the data size and ### should not exceed 32767. Unlike other modes, this mode is special and does not have the 32767 size limitation. The data must have the following structure - Header and Picture data. The values in this mode are little endians. Header Picture data 94 bytes Picture data length File Length Byte position 0 - 1 2 - 3 4 - 7 8 - 11 12 - 13 14 - 15 16 - 19 20 - 21 22 - 55 56 - 59 60 - 61 62 - 63 64 - 65 66 - 67 68- 69 Data 6E 6E 0A 00 5E 00 00 00 File length 01 00 01 00 4A 00 00 00 Compression mode 00 ... 00 Picture data length 01 00 01 00 Pixels/line Pixels/line Lines/picture Description 'nn' This is header ID. Reserved Picture data start offset from header top File length including 94 Byte header. If file length is 65,536 byte, these 4 bytes become "00 00 01 00" Reserved Reserved Reserved 02 00: Fax MH format 03 00: Fax MR format 04 00: Fax G4 format All zero If picture data length is 65,442 (65,536 ~-94) byte, these 4 bytes become "A2 FF 00 00." bit / pixel bit / pixel If picture dot width = 2,400, these 2 bytes become "60 09" Same as above. If picture dot count = 3,100, these 2 bytes become "1C 0C." CHAPTER 2 "PCL" - 83