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125Chapter 9 Remote I/O Scanner Datagrams
Read Map
Subfunction Code: 2A hex
This datagram is used to read the Series 90–70 I/O references assigned to a Remote
I/O Scanner, and its Remote Drop ID.
Data Field Format: none
Read Map Reply
Subfunction Code: 2B hex
A Remote I/O Scanner sends this reply datagram after receiving a Read Map
datagram. It contains the Series 90–70 I/O references assigned to the Remote I/O
Scanner, and its Remote Drop ID. It provides no information about the I/O
assignments of individual I/O modules in the remote drop. However, the checksum
supplied indicates that the overall configuration remains unchanged.
Byte No. Byte Description
0 Remote Drop ID
1 Starting reference %I (LSB)
2 Starting reference %I (MSB)
3 Length of %I data (in bytes)
4, 5 Starting reference %AI
6 Length of %AI data (in bytes)
7, 8 Starting reference %Q
9 Length of %Q data (in bytes)
10,11 Starting reference %AQ
12 Length of %AQ data (in bytes)
13 8–bit Additive Checksum READ ONLY
14, 15 16–bit LRC Checksum (lsb in 14, msb in 15) READ ONLY
The Remote Drop ID is a unique number between 16 and 254 that identifies the remote
drop.
Starting references in %I, %AI, %Q, and %AQ memory may be returned. For each
memory type, a data length is also supplied. If zero, the associated starting reference
can be ignored; it is not meaningful.
Write Map
Subfunction Code: 2C hex
This datagram allows a CPU to send Series 90–70 I/O addresses and a Remote Drop ID
to a Remote I/O Scanner. If the Remote I/O Scanner receives this message, and its
configuration is not currently protected (by means of the Hand–held Monitor’s Con-
figuration Protect feature), the I/O modules present in the remote drop are automati-
cally configured. Data format for this datagram is the same as Read Map Reply.
The checksum must be included in the message, even though its values are ignored.