C504 Datasheet, PDF (10/49 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C504
Table 1
Pin Definitions and Functions (cont’d)
Symbol
COUT3
Pin Number I/O
(P-MQFP-44) *)
28
O
EA
29
I
P0.0-P0.7 37-30
I/O
V_AREF
38
–
V_AGND
39
–
V_SS
16
–
V_CC
17
–
*) I = Input
O = Output
Function
10-Bit compare channel output
This pin is used for the output signal of the 10-bit compare
timer 2 unit. COUT3 can be disabled and set to a high or
low state.
External Access Enable
When held at high level, instructions are fetched from the
internal ROM (C504-2R only) when the PC is less than
4000H.When held at low level, the C504 fetches all
instructions from external program memory.
For the C504-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-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 resistors when issuing 1 s.
Port 0 also outputs the code bytes during program
verification in the C504-2R. External pullup resistors are
required during program (ROM) verification.
Reference voltage for the A/D converter.
Reference ground for the A/D converter.
Ground (0V)
Power Supply (+5V)
Semiconductor Group
10