The PCL has two inputs, IADV and ICRN which control the response to MS codes for Data Operations. When both inputs are low, MS=0 to 3 operations are accepted and MS=4 to 7 are rejected with an SS=6 response, as per the FASTBUS Specification. See Table 26.
When ICRN is high, MS=4 Write Operations on DS(u) are accepted with SS=0 and no other action. MS=4 Write Operations on DS(d) are treated as Clean Up Cycles. MS4 Read Operations are rejected with SS=6. See Table 27.
When IADV is high, MS=4 to 7 Operations are accepted and perform functions as shown in Table 28. These Operations are not FASTBUS standard and are not covered by the FASTBUS Specification. They were arrived at after much discussion by informed FASTBUS users as a useful extension to the standard FASTBUS Operation set. Any of these Operations may be individually suppressed by applying IAC=2 to the PCL when OMS corresponds to the operation not required. The PCL will then respond with SS=6, and suppress the user strobes, etc. .
When both ICRN and IADV are high, the Advanced Modes are available but MS4 Write Operations are as for the ICRN Mode rather than the IADV Mode. See Table 29.
The following abbreviations are used in Tables 26 through 29: