Reference Manual

Turbo PMAC/PMAC2 Software Reference

Turbo PMAC Global I-Variables 76

I83 specifies which MACRO ICs on Turbo PMAC2 control their own independent rings so independent

checking of ring communications using variables I80 to I82 is done using registers in that MACRO IC.

I83 is a 4-bit value. Bit n of I83 corresponds to MACRO IC n. If bit n is set to 1, ring checking is

performed using registers in MACRO IC n. If bit n is set to 0, no ring checking is performed using

registers in MACRO IC n. (However, if all bits are 0, checking can still be done on MACRO IC 0; see

below.)

I80 must be set greater than 0 to specify a ring-check period and activate any ring checking. If I80 is set

greater than 0, ring checking is done automatically on MACRO IC 0, so bit 0 if I83 is not used. However,

if multiple rings are used, it is recommended that Bit 0 be set to 1 for clarity’s sake.

Presently, only the UMAC configuration of the Turbo PMAC2 supports multiple rings (through multiple

Acc-5E boards). All other versions of Turbo PMAC2 can only support a single ring and do ring checking

on MACRO IC 0. For these boards, I83 can be left at the default value of 0.

If multiple MACRO ICs share a common ring, the lowest-numbered MACRO IC on the ring should be

used for ring checking. For example, if MACRO ICs 0 and 1 share one ring, and MACRO ICs 2 and 3

share another, bits 0 and 2 of I83 should be set to 1, yielding a value of 5.

I-variables I20 – I23 specify the base addresses of MACRO ICs 0 – 3, respectively. These must be set

correctly in order for the ring-checking function on these ICs to work properly.

The following table shows which MACRO rings are enabled by the I83 bits.

I83 Bit #,

MACRO IC #

Bit Value

I-Variable for

IC Address

I20

I21

I22

I23