The top, bottom, north, south, east, and west field values entered are the coordinates of the edges of the geographic region. The depths, rows and cols field values entered describe the dimensions of the matrix of data to follow. If the bytes field is entered incorrectly an error will be generated suggesting a closer bytes value.
Have a look at r3.out.ascii to manual page that describes the internal layout of the 3D raster maps and the supported row and depth switch options.
Import of little and big endian byte order as well as signed and unsigned integer data types is supported.
g.region w=0 e=180 s=0 n=90 b=0 t=100 res3=10 r3.mapcalc expr="test_out_bin_float = float(if(row() == 2, null(), row()))" r3.out.bin input=test_out_bin_float byte=4 null=-9999 \ output=test_out_bin_float_native_b4.bin order=native r3.in.bin output=test_in_bin_float byte=4 null=-9999 \ input=test_out_bin_float_native_b4.bin order=native \ bottom=0 top=100 west=0 east=180 south=0 north=90 \ cols=18 rows=9 depths=10