Philips Semiconductors Product data
80C552/83C552
Single-chip 8-bit microcontroller with 10-bit A/D,
capture/compare timer, high-speed outputs, PWM
2002 Sep 03
8
PIN DESCRIPTION (Continued)
PIN NO.
MNEMONIC PLCC QFP TYPE NAME AND FUNCTION
V
SS
36, 37 34-36 I Two Digital ground pins.
PSEN 47 48 O Program Store Enable: Active-low read strobe to external program memory.
ALE 48 49 O Address Latch Enable: Latches the low byte of the address during accesses to external
memory. It is activated every six oscillator periods. During an external data memory
access, one ALE pulse is skipped. ALE can drive up to eight LS TTL inputs and handles
CMOS inputs without an external pull-up.
EA 49 50 I External Access: When EA is held at TTL level high, the CPU executes out of the internal
program ROM provided the program counter is less than 8192. When EA
is held at TTL
low level, the CPU executes out of external program memory. EA is not allowed to float.
AV
REF–
58 59 I Analog to Digital Conversion Reference Resistor: Low-end.
AV
REF+
59 60 I Analog to Digital Conversion Reference Resistor: High-end.
AV
SS
60 61 I Analog Ground
AV
DD
61 63 I Analog Power Supply
NOTE:
1. To avoid “latch-up” effect at power-on, the voltage on any pin at any time must not be higher or lower than V
DD
+ 0.5 V or V
SS
– 0.5 V,
respectively.
OSCILLATOR CHARACTERISTICS
XTAL1 and XTAL2 are the input and output, respectively, of an
inverting amplifier. The pins can be configured for use as an on-chip
oscillator, as shown in the logic symbol, page 2.
To drive the device from an external clock source, XTAL1 should be
driven while XTAL2 is left unconnected. There are no requirements
on the duty cycle of the external clock signal, because the input to
the internal clock circuitry is through a divide-by-two flip-flop.
However, minimum and maximum high and low times specified in
the data sheet must be observed.
RESET
A reset is accomplished by holding the RST pin high for at least two
machine cycles (24 oscillator periods), while the oscillator is running.
To insure a good power-on reset, the RST pin must be high long
enough to allow the oscillator time to start up (normally a few
milliseconds) plus two machine cycles. At power-on, the voltage on
V
DD
and RST must come up at the same time for a proper start-up.
IDLE MODE
In the idle mode, the CPU puts itself to sleep while some of the
on-chip peripherals stay active. The instruction to invoke the idle
mode is the last instruction executed in the normal operating mode
before the idle mode is activated. The CPU contents, the on-chip
RAM, and all of the special function registers remain intact during
this mode. The idle mode can be terminated either by any enabled
interrupt (at which time the process is picked up at the interrupt
service routine and continued), or by a hardware reset which starts
the processor in the same manner as a power-on reset.
POWER-DOWN MODE
In the power-down mode, the oscillator is stopped and the
instruction to invoke power-down is the last instruction executed.
Only the contents of the on-chip RAM are preserved. A hardware
reset is the only way to terminate the power-down mode. The control
bits for the reduced power modes are in the special function register
PCON. Table 1 shows the state of the I/O ports during low current
operating modes.
ROM CODE PROTECTION (83C552)
The 83C552 has an additional security feature. ROM code
protection may be selected by setting a mask–programmable
security bit (i.e., user dependent). This feature may be requested
during ROM code submission. When selected, the ROM code is
protected and cannot be read out at any time by any test mode or by
any instruction in the external program memory space.
The MOVC instructions are the only instructions that have access to
program code in the internal or external program memory. The EA
input is latched during RESET and is “don’t care” after RESET
(also if the security bit is not set). This implementation prevents
reading internal program code by switching from external program
memory to internal program memory during a MOVC instruction or
any other instruction that uses immediate data.
Table 1. External Pin Status During Idle and Power-Down Modes
MODE
PROGRAM
MEMORY
ALE PSEN PORT 0 PORT 1 PORT 2 PORT 3 PORT 4
PWM0/
PWM1
Idle Internal 1 1 Data Data Data Data Data 1
Idle External 1 1 Float Data Address Data Data 1
Power-down Internal 0 0 Data Data Data Data Data 1
Power-down External 0 0 Float Data Data Data Data 1
