Motorola MPC8260 - Manual (Page 190)

5-6 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part II. ConÞguration and Reset
5.4 Reset ConÞguration
Various features may be conÞgured during hard reset or power-on reset. For example, one
conÞgurable features is core disable, which can be used to conÞgure a system that uses two
MPC8260s, one a slave device and the other a the host with an active core. Most
conÞgurable features are reconÞgured whenever HRESET is asserted. However, the clock
mode is conÞgured only when PORESET is asserted.
The 32-bit hard reset conÞguration word is described in Section 5.4.1, ÒHard Reset
ConÞguration Word.Ó The reset conÞguration sequence is designed to support a system that
uses up to eight MPC8260 chips, each conÞgured differently. It needs no additional glue
logic for reset conÞguration.
The description below explains the operation of this sequence with regard to a multiple-
MPC8260 system. This and other simpler systems are described in Section 5.4.2, ÒHard
Reset ConÞguration Examples.Ó In a typical multi-MPC8260 system, one MPC8260
should act as the conÞguration master while all other MPC8260s should act as
conÞguration slaves. The conÞguration master in the system typically reads the various
conÞguration words from EPROM in the system and uses them to conÞgure itself as well
as the conÞguration slaves. How the MPC8260 acts during reset conÞguration is
determined by the value of the RSTCONF input while PORESET changes from assertion
to negation. If RSTCONF is asserted while PORESET changes, MPC8260 is a
conÞguration master; otherwise, it is a slave.
In a typical multiple-MPC8260 system, RSTCONF input of the conÞguration master
should be hard wired to ground, while RSTCONF inputs of other chips should be connected
to the high-order address bits of the conÞguration master, as described in Table 5-5.
The conÞguration words for all MPC8260s are assumed to reside in an EPROM connected
to CS0 of the conÞguration master. Because the port size of this EPROM is not known to
the conÞguration master, before reading the conÞguration words, the conÞguration master
reads all conÞguration words byte-by-byte only from locations that are independent of port
size.
Table 5-5. RSTCONF Connections in Multiple-MPC8260 Systems
ConÞgured Device RSTCONF Connection
ConÞguration master GND
First conÞguration slave A0
Second conÞguration slave A1
Third conÞguration slave A2
Fourth conÞguration slave A3
Fifth conÞguration slave A4
Sixth conÞguration slave A5
Seventh conÞguration slave A6