User’s Manual
C166S V1 SubSystem
The External Bus Interface
User’s Manual
8-30
V 1.6, 2001-08
Precautions and Hints
• The external bus interface is enabled as long as at least one of the BUSCON registers
has its BUSACT bit set.
• PORT1 will output the intra-segment address as long as at least one of the BUSCON
registers selects a demultiplexed external bus, even for multiplexed bus cycles.
• The address windows defined via registers ADDRSELx may overlap internal address
areas. Internal accesses will be executed in this case.
• For any access to an internal address area, the EBC will remain inactive (see
Section 8.5
EBC Idle State).
8.5
EBC Idle State
When the external bus interface is enabled, but no external access is currently being
executed, the EBC is idle. As long as only internal resources (from an architecture point
of view) such as DPRAM, GPRs, or SFRs, etc. are used, the external bus interface does
not change (see
Table 8-7
below).
Accesses to on-chip X-Peripherals are also controlled by the EBC. However, even
though an X-Peripheral appears to the controller as if it were an external peripheral, the
accesses do not generate valid external bus cycles.
Bit
Function
WRC
Write Configuration
0:
Pins WR and BHE operate as WRL and WRH signals
1:
Pins WR and BHE operate as WR and BHE signals
CSSEL
Chip Select Line Selection (Number of active CS outputs)
00:
3 CS lines: CS2...CS0
01:
2 CS lines: CS1...CS0
10:
No CS lines at all
11:
4 CS lines: CS3...CS0 (Default without put-downs)
SALSEL
Segment Address Line Selection (Nr. of active segment addr. outputs)
00:
4-bit segment address: A19...A16
01:
No segment address lines at all
10:
6-bit segment address: A21...A16
11:
2-bit segment address: A17...A16 (Default without put-downs)
CLKCFG
Clock Generation Mode Configuration
These pins define the clock generation mode, i.e. the mechanism how
the internal CPU clock is generated from the externally applied (XTAL1)
input clock.
Содержание C166S V1 SubSystem
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Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
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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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