Printronix P9000 Series - Manual (Page 93)

5-13 Vertical Format Units
Relative Line Slewing
Another method of moving paper using the PI line results in vertical slews of a specified numĆ
ber of lines within the form relative to the current print line (rather than slewing to a specific
line). For this to occur, three criteria must be met:
1. PI line must be set high;
2. Data bit 5 must be 1 (set); and
3. The NVFU must be the selected Vertical Format Unit.
The Slew Relative configuration and the status of data bits 7-6 and 1-4 determine the numĆ
ber of lines slewed as described in Table 5-9. (Note that the state of data bit 5 is the difference
between line slewing and using the interface lines as NVFU channel codes.) As long as the
NVFU is selected, this type of vertical paper motion will occur regardless of whether the
NVFU memory is loaded or not.
If the Double High for One Line attribute is active, n + 1 lines will be slewed rather than n lines.
Table 5-9. NVFU Line Slewing
1 2 3 4 5 6 7 8 PI Line
Bits of Data Byte
1
1
X
X
0
n6 n5
0 1
1
0
n4
0
n3
0
n2
0
n1
X = don't care (1 or 0)
Perform a CR function *
Slew 1 - 63 lines
n1 - n6 = decoded for 1 to 63 line movement
*treated as CR = CR; refer to the Carriage Return control code on page 6-16.
CVFU
The CVFU may be selected in P-Series protocol. The CVFU provides 12 channels to identify
up to 126 lines, responding to Centronics Direct Access Format Unit control codes. This VFU
does not make use of the PI line for either loading or executing. The programming sequence is
1) start load code; 2) line identification code; and 3) end load code.
Start Load Code - 1D Hex
The start load code clears and initializes the CVFU memory for the memory load program. The
start load code is 1D hex. Subsequent data received after the start load code are interpreted as
line identification codes until the end load code is received.
Channel Assignment
Following the start load code, all data bytes received are interpreted as channel assignment
data until the end load code is received.