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6-25
I/O PORTS
6.5.3
EPORT Considerations
This section outlines considerations for using the EPORT pins.
6.5.3.1
EPORT Status During Reset, CCB Fetch, Idle, Powerdown, and Hold
During reset, the EPORT pins are forced to their extended-address functions and are weakly
pulled high. During the CCB fetch, FFH is strongly driven onto the pins. This value remains
strongly driven until either the pin is configured for I/O or a different extended address is access-
ed. If the pins remain configured as extended-address functions, they are placed in a high-imped-
ance state during idle, powerdown, and hold. If they are configured as I/O, they retain their I/O
function during those modes. Table 6-19 shows the status of EPORT pins during reset, CCB fetch,
idle, powerdown, and hold.
6.5.3.2
EP_REG Settings for Pins Configured as Extended-address Signals
Nonextended data accesses go to the address contained in EP_REG. Therefore, if you configure
EP_REG to point to the desired address, you can use nonextended addressing modes to access
the extended address space. However, we recommend that you clear the EP_REG bits for any
EPORT pins configured as extended-address signals in order to maintain compatibility with soft-
ware development tools.
NOTE
If any pins are configured as extended-address signals and their corresponding
EP_REG bits are set, nonextended operations will still access the register file
and standard SFRs. However, all other nonextended accesses, including those
to internal RAM, memory-mapped SFRs, and internal nonvolatile memory,
will be directed off-chip to the “page” address in EP_REG.
Table 6-19. EPORT Pin Status During Reset, CCB Fetch, Idle, Powerdown, and Hold
Pin Name
During Reset
During CCB
Fetch
During Idle, Powerdown, and Hold
A16–A19 (extended address)
weak pull-ups
FFH (Note 1)
high impedance
EPORT.0–EPORT.3 (I/O)
(Note 2)
complementary or open-drain I/O
retains value (no change)
NOTES:
1.
Strongly driven. After the CCB fetch is complete, the value remains until either the pin is configured
for I/O or a different extended address is accessed.
2.
The I/O function is unavailable until after the CCB fetch is completed, at which time the EPORT pins
may individually be configured for either I/O or extended-address function.
Содержание 8XC196NT
Страница 1: ...8XC196NT Microcontroller User s Manual...
Страница 2: ...8XC196NT Microcontroller User s Manual June 1995 Order Number 272317 003...
Страница 22: ...1 Guide to This Manual...
Страница 23: ......
Страница 35: ......
Страница 36: ...2 Architectural Overview...
Страница 37: ......
Страница 49: ......
Страница 50: ...3 Programming Considerations...
Страница 51: ......
Страница 66: ...4 Memory Partitions...
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Страница 104: ...5 Standard and PTS Interrupts...
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Страница 147: ......
Страница 148: ...6 I O Ports...
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Страница 176: ...7 Serial I O SIO Port...
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Страница 194: ...8 Synchronous Serial I O SSIO Port...
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Страница 212: ...9 Slave Port...
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Страница 232: ...10 Event Processor Array EPA...
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Страница 270: ...11 Analog to digital Converter...
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Страница 292: ...12 Minimum Hardware Considerations...
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Страница 306: ...13 Special Operating Modes...
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Страница 318: ...14 Interfacing with External Memory...
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Страница 362: ...15 Programming the Nonvolatile Memory...
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Страница 408: ...A Instruction Set Reference...
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Страница 476: ...B Signal Descriptions...
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Страница 494: ...C Registers...
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Страница 566: ...Glossary...
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Страница 580: ...Index...
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