The fully static design of the 80C52-BASIC chip allows the user
to reduce system power by reducing the clock frequency from 12 MHz
down to any value, even DC, without loss of data or internal
registers (typical operating frequency for BASIC-52 is 11.0592
MHz). In addition, the 80C52 has two software modes for reduced
activity: Idle Mode, where the CPU is frozen but the serial port,
timers, and interrupt system continue to function; and Power-Down
Mode, where the internal RAM is saved but all other functions are
ceased.
A minimum amount of hardware is required to support the
80C52-BASIC chip. Small systems can be constructed with only an
address latch, 1K byte of external memory, and the appropriate
serial port drivers. With the addition of a transistor, a gate,
and a few passive components, BASIC-52 can program EPROM/EEPROMs
directly. Both standard and fast programming algorithms are
supported.
Software
- Full BASIC interpreter in ROM on a single chip
- BCD floating-point math
- Fast tokenized interpreter
- "Stand-alone" software development
- Interrupts can be handled by BASIC or Assembly Language
- Built-in real-time clock
- Generates all timing necessary to program EPROM and EEPROMs
Hardware
Vcc Circuit supply voltage
AD0-AD7 The multiplexed low-order address and data bus
used during access to external memory. External pull-up resistors
(10k ohm) are required on these pins if BASIC-52 EPROM/EEPROM
programming feature is used.
A8-A15 The high-order address bus used during access to
external memory.
PORT 1 Port 1 is a quasi-bidirectional 8-bit
input/output port. It can be used as a standard parallel I/O port
with the PORT1 command in BASIC-52, or the individual pins of Port
1 can have alternative functions as follows:
PORT 1.0(T2) Can be used as the trigger
input to Timer/Counter #2. A logic 1 must be written to this bit
in order for this function to operate.
PORT 1.1 (T2EX) Can be used as the external input to
Timer/Counter #2. A logic 1 must be written to this bit in order
for this function to operate.
PORT 1.2 (PWM OUTPUT) This pin is used as the Pulse
Width Modulated (PWM) output port when the PWM statement is
executed. The PWM statement can generate pulses of varying
frequency and duty cycle.
PORT 1.3 (ALE DISABLE) This pin is used to disable the
ALE signal to the external latch when the EPROM/EEPROM programming
feature is being used. In a system, this pin is logically ANDed
with ALE.
PORT 1.4 (PROGRAMMING PULSE) This pin provides the
proper programming pulse when programming EPROM/EEPROMs.
PORT 1.5 (PROGRAMMING ENABLE) This pin is used to
enable the programming voltage (Vpp) when programming EPROMs and
remains active low during programming. On EEPROMs that do not
require any special programming voltage, this pin is not used.
PORT 1.6 (DMA ACKNOWLEDGE) When the pseudo-DMA feature
is implemented (as outlined in the BASIC-52 Programmers
Manual), this pin functions as an active-low DMA Acknowledge
output.
PORT 1.7 (LINE PRINTER OUTPUT) This pin functions as a
serial output when the LIST# or PRINT# commands are used in BASIC.
This enables the user to have hard-copy output during program
operation or for program listings.
RESET A logic 1 (>3.5V) on this pin for more than
two machine cycles while the oscillator is running will reset the
device. An internal pull-down resistor permits power-on reset
using only a capacitor connected between this pin and Vcc.
ALE (Address Latch Enable) an output pin that is used
to latch the low-order address byte during read, write, or program
fetch operations to external memory.
PSEN (Program Store Enable) a signal used to enable
external program memory. This pin will remain a logic 1 unless the
user is running an assembly language program in external memory.
XTAL1 Input to the inverting amplifier that forms the
oscillator. This input should be left floating when an external
oscillator is used.
XTAL2 Output of the inverting amplifier that forms the
oscillator and input to the internal clock generator. Receives the
external oscillator signal when an external oscillator is used.
RD This pin is a control that is used to enable read
operations to external data memory.
WR This pin is a control signal that is used to enable
write operations to external data memory.
T1 This pin can be programmed to be an external input
to Timer/Counter 1
T0 This pin can be programmed to be an external input
to Timer/Counter 0
INT1 This is the external interrupt 1 input pin.
Interrupts on this pin may be handled in either BASIC-52 or
assembly language.
INT0/DMA REQUEST This is the external interrupt 0 input
pin. It may optionally be programmed to function as a DMA request
input pin or used by EEPROM devices during programming.
CONSOLE SERIAL OUTPUT This is the serial input pin that
receives data from the console device. Standard serial ASCII codes
consisting of 8-bit data with no parity at standard data rates are
assumed. After RESET in BASIC-52, if desired and if the first
character received is a "space," then BASIC-52 will
perform an auto-baudrate calculation and automatically set the
console serial input to the incoming data rate.
EA When EA is held high, the CPU functions as an 80C52
with a BASIC interpreter executing out of internal program memory
(unless the program counter exceeds 0FFFh). When EA is held low,
the CPU functions as a generic 80C52 and executes only out of
external program memory.
*Note: For complete details of the 80C52-BASIC chips
electrical characteristics and timing diagrams, refer to the
design specification sheet for the 80C52 microcontroller chip.
