Atari ST series Technical Reference Manual page 160

block and put the address of this block in the A6 register be­
fore making the call. The format of the BitBlt parameter block
is shown in Table 7-6.
Table 7-6. The Format of the BitBlt Parameter Block
Name
Offset
00-01
B_WD
B_HT
02-03
04-05 PLANE_CT
06-07
FG_COL
08-09 BG_COL
10-13 OP__TAB
14-15 S_XMIN
16-17 S_YMIN
S_FORM
18-21
S_NXWD
22-23
24-25 S_NXLN
26-27 S_NXPL
28-29 D_XMIN
D_YMIN
30-31
D__FORM
32-35
D_NXWD
36-37
38-39 D__ NXLN
40-41 D__ NXPL
42-45 P__ ADDR
46-47 P__ NXLN
48-49 P__ NXPL
50-51 P__ MASK
52-75 SPACE
152
CHAPTER 7
Description
Block width (in pixels)
Block height (in pixels)
Number of consecutive bit planes
Foreground color (bit 1 of logic op
index)
Background color (bit 1 of logic op
index)
Logic ops for all four combinations of
foreground and background
Left position of source rectangle
Top position of source rectangle
Base address of source image
Offset to next word in source line (in
bytes)
Offset to next line in source plane (in
bytes)
Offset from start of current source
plane to next source plane (in bytes)
(this value is 2 for ST screen images)
Left position of destination rectangle
Top position of destination rectangle
Base address of destination image
Offset to next word in destination line
(in bytes)
Offset to next line in destination plane
(in bytes)
Offset from start of current destination
plane to next destination plane (in
bytes) (this value is 2 for ST screen
images)
Address of pattern image data buffer (0
= no pattern)
Offset to next line in pattern (in bytes)
Offset to next plane in pattern (in
bytes)
Pattern index mask
A buffer the blit operations require for
temporary storage. This space must be
reserved, or the memory which follows
the parameter block will be mangled.