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Print Engine Interface
MOTOROLA
MC68322 USER’S MANUAL
10-5
10.1.3 Printer Control Block Register Set
The printer control block (PCB) register set is a group of six registers that define a print
operation for the PVC to execute. The PCB values define the dimensions and location of the
band image, page margins, and band control data. Loading the page image bit address
portion of the PCB is the stimulus that starts the PVC and begins a print operation. The entire
PCB register set is doubled buffered, which allows two print operations to be loaded at a
time. Basically, when the first operation finishes, the second operation immediately begins
executing. This is especially useful in banding applications.
Figure 10-3. Printer Control Block Register Set
The PCB’s vertical and horizontal margin registers position the page image on the printed
page. The vertical margin value specifies the number of scanlines that are skipped before
the first scanline of page image data and the horizontal margin value defines the number of
internal video clocks that are skipped before the first bit is transmitted at the start of each
scanline.
The PCB’s page image height and width registers describe the limits of the page image as
it is to be read from memory and transmitted to the print engine. The page image height is
measured in scanlines, but the page image width is in bits. The PCB also contains three 1-
bit fields that control the execution of a print operation on a band-by-band basis.
BND—Band
This bit is used during banding applications to indicate when the current band image is to be
followed by another band on a page. It is set for all bands, but cleared for the last band in a
sequence or when only one band appears on a page.
B2T—Bottom to Top
This bit is set to indicate the render direction. When B2T is clear, it indicates a top to bottom
and left to right direction. When set, it indicates a bottom to top and right to left direction.
SME—SmartToner Enable
This bit is used to reduce the amount of toner the printer uses. When it is enabled, a halftone
pattern is applied to the video data sent to the print engine. The print image in memory is
not affected. The SME bit is double buffered and can be set or cleared for a specific page.
15
14
13
12
11
10
9
8
7
65432
1
0
15
14
13
12
11
10
9
8
7
65432
1
0
BND
B2T
SME
VERTICAL MARGIN
00FFF404
00FFF406
00FFF408
00FFF40A
00FFF40C
00FFF410
00FFF412
HORIZONTAL MARGIN
PAGE IMAGE HEIGHT
PAGE IMAGE WIDTH
PAGE IMAGE BIT ADDRESS, LOW WORD
PAGE IMAGE BIT ADDRESS, HIGH WORD
0
RESERVED