SAB80C515A-5 Datasheet, PDF (61/108 Pages) Siemens Semiconductor Group – 8-Bit CMOS Single-Chip Microcontroller Family

SAB 80C515A/83C515A-5
Pin Definitions and Functions (cont’d)
Symbol Pin
Pin
Input (I) Function
P-LCC-68 P-MQFP-80 Output (O)
XTAL1 40
37
-
P2.0-P2.7 41-48
38-45
I/O
PSEN 49
47
O
ALE
50
48
O
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 require-
ments on the duty cycle of the external clock
signal, since the input to the internal clok-
king circuitry is divided down by a divide-by-
two flip-flop. Minimum and maximum high and
low times and rise/fall times specified in the
AC characteristics must be taken into account.
Port 2
is an 8-bit bidirectional I/O port with internal
pullup resistors. Port 2 pins that have 1's
written to them are pulled high by the internal
pullup resistors, and in that state can be used
as inputs. As inputs, port 2 pins being
externally pulled low will source current (I _IL, in
the DC characteristics) because of the internal
pullup 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 pullup
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.
The Program Store Enable
output is a control signal that enables the
external program memory to the bus during
external fetch operations. It is activated every
six oscillator periods, except during external
data memory accesses. The signal remains
high during internal program execution.
The Address Latch enable
output is used for latching the address into
external memory during normal operation. It is
activated every six oscillator periods, except
during an external data memory access.
Semiconductor Group
6-9