C164CM Datasheet, PDF (11/68 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontrol ler

C164CM
C164SM
Table 2
Pin Definitions and Functions (cont’d)
Symbol Pin
No.
Input Function
Outp.
P20
IO
Port 20 is a 6-bit bidirectional I/O port (no P20.5 output driver
in the OTP versions). It is bit-wise programmable for input or
output via direction bits. For a pin configured as input, the
output driver is put into high-impedance state.
The following Port 20 pins also serve for alternate functions:
P20.0 28
O
RD
External Memory Read Strobe, activated for
every external instruction or data read access.
P20.1 29
O
WR
External Memory Write Strobe, activated for
every external data write access.
P20.4 30
O
ALE
Address Latch Enable Output.
Can be used for latching the address into external memory
or an address latch in the multiplexed bus modes.
P20.5 31
I
EA
External Access Enable pin.
A low level at this pin during and after Reset forces the
C164CM to latch the configuration from PORT0 and pin RD,
and to begin instruction execution out of external memory.
A high level forces the C164CM to latch the configuration
from pins RD, ALE, and WR, and to begin instruction
execution out of the internal program memory.
“ROMless” versions must have this pin tied to ‘0’.
–
V_PP
OTP Programming voltage
The OTP versions of the C164CM receive the programming
voltage via this pin. (No output driver for P20.5 in this case!)
P20.8 34
O
CLKOUT System Clock Output (= CPU Clock),
O
FOUT
Programmable Frequency Output
P20.12 35
O
RSTOUT Internal Reset Indication Output. This pin is set
to a low level when the part is executing either a hardware-,
a software- or a watchdog timer reset. RSTOUT remains low
until the EINIT (end of initialization) instruction is executed.
Data Sheet
7
V1.0, 2001-05