IBM RT Series Hardware Reference Manual page 344

TNL SN20-9844 (March 1987) to 75X0235
Graphic Commands
Execute Command
I/O DATA FIELD
o
I
718
15
I I I I I I I I I I I I I
I
I _ _
I
II
I
Figure 20. Execute Command Word (Address X'D9CXXX')
Bits 00-03 EXECUTE DECODE
( 1 1 0 1 )
Bit 04 DECREMENT QUEUE COUNTER FLAG
Bit 05 GRAPHIC OP INTERRUPT FLAG
Bits 06-11 GRAPHIC OP TYPE
Bits 12-15 GRAPHIC OP LOGIC FUNCTION (subtype)
For each graphic operation there is one execute command word. It is designated via the execute
decode B'llOl '.
The execute command word contains a decrement queue counter flag. When this flag is active,
it designates queue load sequence end. If the flag is inactive, more graphic operations must
follow. Before incrementing the queue counter, a complete queue load sequence (decrement
queue counter flag) must be loaded somewhere in the queue list structure.
The graphic op interrupt flag bit, if active, sets the graphic operation interrupt latch at the
completion of the graphic operation. This action can be observed via the graphic operation
interrupt status (bit 3) in the status register. The only way to reset the graphic operation
interrupt latch is via an I/O channel write of a reset graphic operations command or a reset
adapter command. If the graphic operation interrupt enable bit (bit 1) is active in the control
register and the graphic operation interrupt latch is active, then an active interrupt is driven on
the I/O channel. Disabling graphic operation interrupts does not reset the interrupt latch.
The graphic operation type field specifies different graphic operation types. The graphic
operation logic function field specifies a subtype within a graphic operation sequence. See
graphic operations definitions for specifics about each graphic operations type and subtype.
32 Extended Monochrome Graphics Adapter