41-553M.pdf - Pickering Interfaces

6. ERROR INJECTION
This chapter applies only to the 41-553 version C, which can generate specific
errors in its transmissions. This capability is useful for testing the response
of hardware or systems to bus faults. This chapter explains how to use
the 41-553 API to control generation of errors. Three examples demonstrate
how to specify the type, location and frequency of an error.
6.1 Error Injection Overview
Error injection is the act of transmitting a signal that does not comply with
the MIL-STD-1553 specification. Any of the following types of errors may
be injected:
1. Parity: inverts the parity bit
2. Sync error: inverts the sync pulse
3. Bit Count: transmits a word with fewer or greater than the normal 20 bit
times.
4. Manchester error: inverts either the first or second half bit in a given bit
position
5. Word count: transmits a specified number of data words, ignoring the
word count field of the command word
6. Gap errors: insert a gap of specified length preceding a word
Error injection is a three-step process. An application program:
1. Defines an error in the 41-553.
2. Tags the message or messages that are candidates to contain the error.
This step is optional.
3. Enables error injection.
The following subsections describe these steps in detail.
6.1.1 Defining the Error
Errors are defined using the L13_ErrorDefine function. Only one error
may be defined on the 41-553 at any given time, and that error is used in all
subsequent error injections. The error may be changed by repeated calls to
L13_ErrorDefine. Table 6-1 shows the parameters required for complete
definition of different types of errors.
Error Type Word position Value Count Bit position
Parity
✔
Sync
✔
Manchester ✔ ✔
Word count
✔
Bit count ✔ ✔ ✔
Gap ✔ ✔
Table 6-1 L13_ErrorDefine parameters according to error type
41-553 User’s Manual 6-1