C167CS datasheet(215/517 Pages) INFINEON

215 / 517 page

C167CS

Derivatives

The External Bus Interface

User’s Manual

9-27

V2.0, 2000-07

Address Window Arbitration

The address windows that can be defined within the C167CS’s address space may

partly overlap each other. Thus e.g. small areas may be cut out of bigger windows in

order to effectively utilize external resources, especially within segment 0.

For each access the EBC compares the current address with all address select registers

(programmable ADDRSELx and hardwired XADRSx). This comparison is done in four

levels.

Priority 1: The hardwired XADRSx registers are evaluated first. A match with one of

these registers directs the access to the respective X-Peripheral using the

corresponding XBCONx register and ignoring all other ADDRSELx regis-

ters.

Priority 2: Registers ADDRSEL2 and ADDRSEL4 are evaluated before ADDRSEL1

and ADDRSEL3, respectively. A match with one of these registers directs

the access to the respective external area using the corresponding BUS-

CONx register and ignoring registers ADDRSEL1/3 (see Figure 9-11).

Priority 3: A match with registers ADDRSEL1 or ADDRSEL3 directs the access to the

respective external area using the corresponding BUSCONx register.

Priority 4: If there is no match with any XADRSx or ADDRSELx register the access to

the external bus uses register BUSCON0.

Figure 9-11

Address Window Arbitration

Note: Only the indicated overlaps are defined. All other overlaps lead to erroneous bus

cycles. E.g. ADDRSEL4 may not overlap ADDRSEL2 or ADDRSEL1. The

hardwired XADRSx registers are defined non-overlapping.

MCA04368

XBCON0

BUSCON2

BUSCON1

BUSCON0

BUSCON4

BUSCON3

Active Window

Inactive Window

C167CS Datasheet(PDF) 215 Page - Infineon Technologies AG