User’s Manual
C166S V1 SubSystem
The External Bus Interface
User’s Manual
8-35
V 1.6, 2001-08
• the C166S needs access to the shared resources and demands this by activating its
BREQ output. The arbitration logic may then deactivate the other master’s HLDA and
so free the external bus for the C166S, depending on the priority of the different
masters.
Note: The Hold State is not terminated by clearing bit HLDEN.
Figure 8-13
External Bus Arbitration, Regaining the Bus
Note: The falling BREQ edge indicates the last chance for BREQ to trigger the regain
sequence. Even if BREQ is activated earlier, the regain sequence is initiated by
HOLD going high. BREQ and HOLD are connected via an external arbitration
circuitry. HOLD may also be deactivated without the C166S requesting the bus.
8.7
The XBUS Interface
The C166S provides an on-chip interface (the XBUS interface) by which integrated
customer/application-specific peripherals can be connected to the standard controller
core. The XBUS is an internal representation of the external bus interface, i.e., it is
operated in the same way.
For each peripheral on the XBUS (X-Peripheral) there is a separate address window
controlled by a register pair XBCONx/XADRSx (similar to registers BUSCONx and
ADDRSELx). Because an interface to a peripheral is represented in many cases by just
a few registers, most of the XADDRSEL registers select smaller address windows than
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
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