C515A_9708 Datasheet, PDF (14/182 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Introduction
C515A
Table 1-1
Pin Definitions and Functions (cont’d)
Symbol
EA
P0.0-P0.7
P5.0-P5.7
HWPD
N.C.
*) I = Input
O = Output
Pin Number I/O*) Function
(P-MQFP-80)
49
I
External Access Enable
When held high, the C515A executes instructions from
the internal ROM (C515A-4R) as long as the PC is less
than 8000H. When held low, the C515A fetches all
instructions from external program memory. For the
C515A-L this pin must be tied low.
52-59
I/O Port 0
is an 8-bit open-drain bidirectional I/O port. Port 0 pins
that have 1's 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 and data
memory. In this application it uses strong internal pullup
resistors when issuing 1's. Port 0 also outputs the code
bytes during program verification in the C515A-4R.
External pullup resistors are required during program
verification.
67-60
I/O Port 5
is an 8-bit quasi-bidirectional I/O port with internal pullup
resistors. Port 5 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 5 pins being
externally pulled low will source current (I _IL, in the DC
characteristics) because of the internal pullup resistors.
69
I
Hardware Power Down
A low level on this pin for the duration of one machine
cycle while the oscillator is running resets the C515A. A
low level for a longer period will force the C515A into
Hardware Power Down Mode with the pins floating.
2, 13, 14, 23, –
46, 50, 51, 68,
70, 71
Not connected
These pins of the P-MQFP-80 package need not be
connected.
Semiconductor Group
1-9
1997-08-01