SAB80C517 Datasheet, PDF (11/61 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller

SAB 80C517/80C537
Pin Definitions and Functions (cont’d)
Symbol
Pin Number
I/O ^*) Function
P-LCC-84 P-MQFP-100-2
XTAL2
39
12
XTAL1
40
13
P2.0 - P2.7 41 - 48
14 - 21
* _{I = Input}
O = Output
– XTAL2
Input to the inverting oscillator amplifier
and input to the internal clock generator
circuits.
– XTAL1
Output of the inverting oscillator
amplifier. To drive the device from an
external clock source, XTAL2 should
be driven, while XTAL1 is left
unconnected. There are no
requirements on the duty cycle of the
external clock signal, since the input to
the internal clocking circuitry is devided
down by a divide-by-two flip-flop.
Minimum and maximum high and low
times as well as rise/fall times specified
in the AC characteristics must be
observed.
I/O Port 2
is a bidirectional I/O port with internal
pull-up resistors. Port 2 pins that have
1 s written to them are pulled high by
the internal pull-up resistors, and in that
state can be used as in-puts. As inputs,
port 2 pins being externally pulled low
will source current (I_IL, in the DC
characteristics) because of the internal
pull-up resistors. Port 2 emits the high-
order address byte during fetches from
external program memory and during
accesses to external data memory that
use 16-bit addresses (MOVX @DPTR).
In this application it uses strong
internal pull-up resistors when issuing
1 s. During accesses to external data
memory that use 8-bit addresses
(MOVX @Ri), port 2 issues the
contents of the P2 special function
register.
Semiconductor Group
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