SAF-C502-2R20N Siemens Semiconductor Group, SAF-C502-2R20N Datasheet - Page 11

• Manufacturer Part Number: SAF-C502-2R20N
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: Siemens Semiconductor Group

Pin Definitions and Functions (cont’d)
Symbol
RESET
ALE
EA
P0.0 – P0.7
V
V
N.C.
*) I = Input
Semiconductor Group
SS
CC
O = Output
P-LCC-44
10
33
35
43–36
22
44
1, 12,
23, 34
Pin Number
P-DIP-40
9
30
31
39–32
20
40
–
I/O*)
I
O
I
I/O
–
–
–
10
Function
RESET
A high level on this pin for two machine cycles
while the oscillator is running resets the
device. An internal diffused resistor to
permits power-on reset using only an external
capacitor to
The Address Latch Enable
output is used for latching the low-byte of the
address into external memory during normal
operation. It is activated every six oscillator
periodes except during an external data
memory access.
External Access Enable
When held at high level, instructions are
fetched from the internal ROM (SAB-C502-2R
only) when the PC is less than 4000 H . When
held at low level, the SAB-C502 fetches all
instructions from external program memory.
For the SAB-C502-L this pin must be tied low.
Port 0
is an 8-bit open-drain bidirectional I/O port.
Port 0 pins that have 1s written to them float,
and in that state can be used as high-
impedance inputs. Port 0 is also the
multiplexed low-order address and data bus
during accesses to external program or data
memory. In this application it uses strong
internal pull-up resistors when issuing 1s.
Port 0 also outputs the code bytes during
program verification in the SAB-C502-2R.
External pull-up resistors are required during
program verification.
Circuit ground potential
Supply terminal for all operating modes
No connection
V
CC
.
V
SS
C502