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HP 2500 HP PCL/PJL reference - Printer Job Language Technical Reference Manual - Page 216

Printer Status Readback and Printer I/O Switching

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However, under some conditions the application will send, or attempt to send, a PJL ECHO command and not receive a timely response because of one of two reasons: the printer may not be accepting data (due to the printer processing a print job from a different I/O interface or the printer being off-line), or the printing system does not support printer status readback to the application. If the application does not receive a response within three seconds, then the application can assume printer status readback is currently unavailable. In some printing environments, the application may be able to distinguish between the host operating system not being able to send the query, and the query being sent without receiving a response in a reasonable amount of time. Application developers should not assume that because a query was sent and a response was not received in a timely fashion, that the printer system does not support bi-directional communication. Printer sharing devices may buffer the query and the response may be available, however the data buffered before the query may take more than three seconds to process, delaying the response by more than three seconds. The application should notify the user that printer status readback is currently unavailable and query the user to determine how to proceed. The common choices are: 1) printer busy, continue retrying until printer status readback is available, 2) printer busy on a long printer job, temporarily do not use printer status readback, or 3) printer status readback unavailable due to host-printer configuration, do not use printer status readback. After obtaining the user's response, the application can continue as appropriate. Printer Status Readback and Printer I/O Switching I/O switching occurs when a printer contains more than one I/O interface and accepts data from any interface, based on a first-come first-served basis. Some PJL printers do not support I/O switching. I/O switching adds complexity to printing solutions taking advantage of printer status readback. If the printer is currently processing a print job from a different I/O interface, applications querying the printer will have to wait for the printer to respond to the query, (or proceed without using printer status readback). The amount of time until the printer provides the response is dependent on the length of the current print job and the length of any other print jobs the printer may process before processing the application's query. 11-22 Programming Tips for Using PJL EN

Section	Page
Main Menu	3
Inside This Manual	5
Manual Organization	6
Related Documents	9
Manual Conventions	10
Contents	11
Introduction to PJL	15
What is PJL?	15
The Benefits of PJL	17
Who Should Use PJL?	17
Compatibility With Non-PJL Printers	18
PJL Command Syntax and Format	21
Introduction	21
Syntax Conventions	22
Format of PJLCommands	24
PJL Syntax Rules	25
Types of Variables	27
Processing Invalid Commands	29
Using PJL	31
Introduction	31
Overview of How Commands are Used	31
PJL Job Requirements	33
Some Sample PJLJobs	34
What's Next?	35
Command Groupings by Functionality	36
Kernel Commands	41
Introduction	41
Universal Exit Language (UEL) Command	42
ENTER Command	44
COMMENT Command	46
Methods of Printer Language Switching	47
Job Separation Commands	49
Introduction	49
JOB Command	50
EOJ Command	56
PJL Job Security	58
Password Protection of Default Feature Settings	58
Control Panel Lock	59
Disk Lock	59
Job Cancellation	61
Start of Job Notification	61
End of Job Notification	62
Job Cancellation Unsolicited Status	63
Environment Commands	65
Introduction	65
Print Environments	66
Changing Environment Settings	69
Environment Summary	70
PJL Reset Conditions	72
Key Points to Remember About Environments	74
PJL Environment Variables	75
General PJL Environment Variables	76
Port-Specific Variables (LaserJet4PJ Only)	90
PCL-Specific Variables	91
PostScript-Specific Variables	95
ESC/P-Specific Variables	96
Setting the Printer to a Desired State	98
DEFAULT Command	100
INITIALIZE Command	103
RESET Command	106
SET Command	109
Status Readback Commands	113
Introduction	113
Printer Status Requirements	115
Synchronizing Status Readback Responses	115
Format of Status Readback Responses	116
INQUIRE Command	117
DINQUIRE Command	122
ECHO Command	126
INFO Command	128
USTATUS Command	143
TIMED Variable	152
USTATUSOFF Command	154
Job Recovery	155
Sending the Initial Job	155
After Job Failure	156
Device Attendance Commands	159
Introduction	159
RDYMSG Command	160
OPMSG Command	163
STMSG Command	165
PJL File System Commands	169
Introduction	169
FSAPPEND Command	171
FSDIRLIST Command	173
FSDELETE Command	175
FSDOWNLOAD Command	176
FSINIT Command	177
FSMKDIR Command	178
FSQUERY Command	179
FSUPLOAD Command	181
File System Example	183
Job Management	187
Introduction	187
HP LaserJet 8100 Printer	187
HP LaserJet 8500 Printer	191
Programming Tips for Using PJL	195
Introduction	195
PJL Services	196
Print Data Generators	197
Printer Utilities	199
Spoolers	205
Requesting Printer Status	212
Using Status Readback in a Multi-User System	212
Product-Specific Feature Support	223
Introduction	223
PJL Feature Support	224
PJL Environment Variable Support	228
HP LaserJet IIISi Comments	265
Comments about HP LaserJet Printers	266
LaserJet Printers with Reduced-Function Control Panels	273
Color LaserJet Printer Comments	274
HP DeskJet 1200C and 1600C Printer Family Comments	274
HP LaserJet 5Si/ 5SiMx/5Si Mopier Comments	278
HP LaserJet 5Si Mopier Comments	279
HP LaserJet 4000 and 5000 Series Comments	281
HP LaserJet 1100 Series Comments	283
HP LaserJet 2100 Series Comments	284
HP Color LaserJet 4500 Series Comments	285
HP LaserJet 8000 and 8100 Series Comments	286
HP Color LaserJet 8500 Series Comments	287
PJL Command Summary	289
Programming Examples	295
Introduction	295
PJL Status Codes	301
Status Code Groupings	301
Informational Messages (10xxx) *	302
Background Paper Loading (11xyy)	304
Background Paper Tray Status (12xyy)	306
Output Bin Status (15xxy)	307
PJL Parser Errors (20xxx)	307
PJL Parser Warnings (25xxx)	309
PJL Semantic Errors (27xxx)	310
Auto-Continuable Conditions (30xxx)	311
PJL File System Errors (32xxx)	313
Potential Operator Intervention Conditions (35xxx)	314
Operator Intervention Conditions (40xxx)	316
Foreground Paper Loading (41xyy)	319
Paper Jam Messages (LaserJet 5Si/5SiMx only) (42xyy)	320
Optional (External) Paper Handling Device Messages (43xyy)	322
LaserJet 4000 / 5000 Series Paper Jam Messages (44xyy)	323
Hardware Errors (50xxx)	324
Glossary	327
Index	335
Symbols	335
Numerics	335
A	335
B	335
C	335
D	335
E	336
F	336
H	336
I	336
J	337
K	337
L	337
M	337
N	337
O	337
P	338
Q	339
R	339
S	339
T	339
U	339
V	340

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11-22

Programming Tips for Using PJL

However, under some conditions the application will send, or attempt

to send, a PJL ECHO command and not receive a timely response

because of one of two reasons: the printer may not be accepting data

(due to the printer processing a print job from a different I/O interface

or the printer being off-line), or the printing system does not support

printer status readback to the application. If the application does not

receive a response within three seconds, then the application can

assume printer status readback is currently unavailable.

In some printing environments, the application may be able to

distinguish between the host operating system not being able to send

the query, and the query being sent without receiving a response in a

reasonable amount of time. Application developers should not

assume that because a query was sent and a response was not

received in a timely fashion, that the printer system does not support

bi-directional communication. Printer sharing devices may buffer the

query and the response may be available, however the data buffered

before the query may take more than three seconds to process,

delaying the response by more than three seconds.

The application should notify the user that printer status readback is

currently unavailable and query the user to determine how to

proceed. The common choices are: 1) printer busy, continue retrying

until printer status readback is available, 2) printer busy on a long

printer job, temporarily do not use printer status readback, or 3)

printer status readback unavailable due to host-printer configuration,

do not use printer status readback. After obtaining the user's

response, the application can continue as appropriate.

Printer Status Readback and Printer I/O Switching

I/O switching occurs when a printer contains more than one I/O

interface and accepts data from any interface, based on a first-come

first-served basis. Some PJL printers do not support I/O switching.

I/O switching adds complexity to printing solutions taking advantage

of printer status readback. If the printer is currently processing a print

job from a different I/O interface, applications querying the printer will

have to wait for the printer to respond to the query, (or proceed

without using printer status readback). The amount of time until the

printer provides the response is dependent on the length of the

current print job and the length of any other print jobs the printer may

process before processing the application's query.