Compuprint 4247-Z03 Programmer Manual - Manual (Page 103)

DATA is the field that follows the correlation ID field or the flag byte if no correlation ID is present. The
length of this field can be 0-250 (X'00'-X'FA') if no correlation ID is present, and 0-248 (X'00'-X'F8') if the
correlation ID is present.
The first byte of the data field is the acknowledgment type. Values of 00, 01, 04, and 06 for this byte
indicate a positive acknowledgment (ACK). A value of X'80' for this byte indicates a negative
acknowledgment (NACK). Any other values for this byte are invalid.
The next 4 bytes of the data field are the page/copy counters. The first two page/copy counter bytes
(most significant bytes) are a stacked page counter. This counter identifies how many pages have
successfully stacked and printed. The last two page/copy counter bytes (least significant bytes) are
reserved and must be zero.
Following the page/copy counter bytes is the Special Data (SD) area. Depending on the acknowledgment
type, this field can be omitted, can contain requested printer information, or can contain sense information.
The following chart summarizes the acknowledgments and the special data areas:
Type Meaning Special Data Area Contents
X'00' ACK None
X'01' ACK Type and Model
X'04' ACK Resource List
X'06' ACK Printer Information
X'80' NACK Sense Bytes
For a detailed explanation of the Special Data (SD) area contents, see Chapter 4, “IPDS Programming
Information,” on page 99.
Host Acknowledgment Requests
The host requests an acknowledgment from the printer by setting the Acknowledgment Required (ARQ)
flag bit on in the IPDS command (see “IPDS Command Format” on page 80). This request occurs in two
instances:
1. In any command of a command sequence when the host wants a positive acknowledgment (ACK) that
the printer has received and accepted the command sequence for processing.
2. In commands sent by the host to request the return of printer information.
If the printer receives a command that is normally used to request the return of printer data but the ARQ
flag is not on, the printer ignores this command.
A positive acknowledgment (ACK) at the end of a command stream is equivalent to an ACK on each and
every command preceding the command that has the ACK. An ACK is an indication from the printer that
all commands since the last acknowledgment are accepted for processing.
Printer Acknowledgment Replies
The printer sends an Acknowledge Reply to the host to:
v Indicate that a received command or command sequence requesting acknowledgment has been
accepted for processing
v Return requested printer information
v Report errors.
Chapter 3. Intelligent Printer Data Stream 83