snap ethernet-based i/o units protocols and programming guide

Data Log—Read/Write
(Does not apply to SNAP Simple I/O) Use this section to access data logged from memory map
addresses set up in “Data Logging Configuration—Read/Write” on page 146. The data from all
addresses goes into one data log file. The data log is a circular buffer; it holds 300 samples of 14
bytes (hex) per entry, and the newest data item replaces the oldest one. See “Logging Data” on
page 37 for more information on data logging, and see page 38 for how to interpret information
from these data log addresses.
Although this area is read/write, you would normally read it only. You could write to it to clear it,
however.
Starting Address Length Type Description
FFFF F302 0000 14 * First entry in the data log
FFFF F302 0014 14 * Second entry in the data log
Additional entries follow in order.
FFFF F302 175C 14 * Last entry in the data log
Last valid address in this area: FFFF F302 176F
* Binary data. See page 38.
PID Module Configuration—Read/Write
(Does not apply to SNAP Simple I/O) Use this area to configure PID modules on the rack. To
configure PID loops to run on the brain, see page 142.
The table shows addresses for a PID module in rack position zero. Modules in other positions on
the rack follow the same pattern and start on even 100 hex boundaries.
CAUTION: Values for many of these memory map addresses require you to calculate them in
advance. Some values are read-only and cannot be changed. For explanations and important
information on using these addresses, see Opto 22 form 1263, the SNAP PID Module User’s
Guide.
Starting Address Length Type Description
FFFF F400 0000 4 I PID module in position 0 on the rack: Control word
FFFF F400 0004 4 I Position 0: State of status flags (read only)
FFFF F400 0008 4 I Position 0: Scantime base (scantime resolution)
FFFF F400 000C 4 I Position 0: Scantime multiplier
FFFF F400 0010 4 I Position 0: TPO period multiplier
SNAP Ethernet-Based I/O Units Protocols and Programming Guide 147