Siemens CPU 948, Руководство по программированию, Страница: 428 / 548

Call parameters For all communication OBs the number of the first flag byte in the
data field (= pointer to data field) in ACCU-1-L is transferred as the
call parameter. Permitted values are 0 to 246.
Example
10.2.8
How to Evaluate the
Output Parameters
Among other things, the output parameters indicate whether or not a
function could be executed and if not they indicate the reason for the
termination of the function.
Condition codes
The INITIALIZE, SEND, SEND TEST, RECEIVE and RECEIVE
TEST functions affect the condition codes (see programming
instructions for your CPUs, general notes on the STEP 5 operations):
••
the OV and OS bits (word condition codes) are always cleared,
••
the OR, STA, ERAB bits (bit condition codes) are always cleared,
••
RLO, CC 1 and CC 0 indicate whether a function has been executed
correctly and completely.
Data field with parameters for the RECEIVE function
(OB 204)
FY x + 0: transmitting CPU input parameter
FY x + 1: — not used
FY x + 2: condition code byte output parameter
FY x + 3: receiving capacity output parameter
FY x + 4: block ID output parameter
FY x + 5: block number output parameter
FY x + 6: address of the first output parameter
FY x + 7: received data word output parameter
FY x + 8: address of the last output parameter
FY x + 9: received data word output parameter
This example illustrates that the number of the first F flag byte in the
data field must not be higher than FY 246, since otherwise the parameter
field of up to 10 bytes would exceed the limits of the flag area (FY 255).
Multiprocessor Communication
CPU 948 Programming Guide
10 - 24
C79000-G8576-C848-04