C511 Datasheet, PDF (11/43 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C511 / C513
Table 3
Pin Definitions and Functions (cont’d)
Symbol
ALE
EA
P0.0-P0.7
V_SS
V_CC
N.C.
Pin Number I/O*) Function
P-LCC- P-MQFP-
44
44
33
27
O 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.
If no external memory is used, the ALE signal generation
can be inhibited, reducing system RFI, by clearing
register bit EALE in the SYSCON register.
35
29
I
External Access Enable
When held at high level, instructions are fetched from the
internal ROM when the PC is less than the size of the
internal ROM : C511
0A00H
C511A
1000H
C513
2000H
C513A/A-H
3000H
C513A-2R
4000H
When held at low level, the microcontroller fetches all
instructions from external program memory.
43-36 37-30
I/O 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-impendance 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 pullup transistors when
issuing 1s. External pullup resistors are required during
program verification.
22
16
– Circuit ground potential
44
38
– Power Supply terminal for all operating modes
1, 12, 6, 17, – No connection, do not connect externally
23, 34 28, 39
*) I = Input
O = Output
Semiconductor Group
11