8XC196L
X SUPPLEMENT
5-2
input signals set SFDIR. Even if a pin is to be used in special-function mode, you must still ini-
tialize the pin as an input or output by writing to the port direction register.
Resistor R1 provides ESD protection for the pin. Input signals are buffered. The standard ports
use Schmitt-triggered buffers for improved noise immunity. Port 5 uses a standard input buffer
because of the high speeds required for bus control functions. The signals are latched into the port
pin register sample latch and output onto the internal bus when the port pin register is read.
The falling edge of RESET# turns on transistor Q3, which remains on for about 300 ns, causing
the pin to change rapidly to its reset state. The active-low level of RESET# turns on transistor Q4,
which weakly holds the pin low. Q4 remains on, weakly holding the pin low, until your software
writes to the port mode register.
NOTE
P2.7 is an exception. After reset, P2.7 carries the CLKOUT signal (half the
crystal input frequency) rather than being held low. When CLKOUT is
selected, it is always a complementary output.
Содержание 87C196CA
Страница 1: ...8XC196Lx Supplement to 8XC196Kx 8XC196Jx 87C196CA User s Manual August 2004 Order Number 272973 003...
Страница 9: ...1 Guide to This Manual...
Страница 10: ......
Страница 13: ...2 Architectural Overview...
Страница 14: ......
Страница 22: ......
Страница 23: ...3 Address Space...
Страница 24: ......
Страница 33: ...4 Standard and PTS Interrupts...
Страница 34: ......
Страница 43: ...5 I O Ports...
Страница 44: ......
Страница 51: ...6 Synchronous Serial I O Port...
Страница 52: ......
Страница 56: ......
Страница 57: ...7 Event Processor Array...
Страница 58: ......
Страница 65: ...8 J1850 Communications Controller...
Страница 66: ......
Страница 89: ...9 Minimum Hardware Considerations...
Страница 90: ......
Страница 93: ...10 Special Operating Modes...
Страница 94: ......
Страница 98: ......
Страница 99: ...11 Programming the Nonvolatile Memory...
Страница 100: ......
Страница 106: ......
Страница 107: ...A Signal Descriptions...
Страница 108: ......
Страница 118: ......
Страница 119: ...Glossary...
Страница 120: ......
Страница 133: ...Index...
Страница 134: ......