ADUC812BS Analog Devices Inc, ADUC812BS Datasheet - Page 29

• Manufacturer Part Number: ADUC812BS
• Description: IC ADC 12BIT MULTICH MCU 52-MQFP
• Manufacturer: Analog Devices Inc
• Series: MicroConverter® ADuC8xxr

Specifications of ADUC812BS

• Rohs Status: RoHS non-compliant
• Core Processor: 8052
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: PSM, Temp Sensor, WDT
• Number Of I /o: 34
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 640 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x12b, D/A 2x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 52-MQFP, 52-PQFP

8051 COMPATIBLE ON-CHIP PERIPHERALS
This section gives a brief overview of the various secondary
peripheral circuits that are also available to the user on-chip.
These remaining functions are fully 8051 compatible and are
controlled via standard 8051 SFR bit definitions.
Parallel I/O Ports 0–3
The ADuC812 uses four input/output ports to exchange data with
external devices. In addition to performing general-purpose I/O,
some ports are capable of external memory operations; others
are multiplexed with an alternate function for the peripheral
features on the device. In general, when a peripheral is enabled,
that pin may not be used as a general-purpose I/O pin.
Port 0 is an 8-bit, open-drain, bidirectional I/O port that is directly
controlled via the P0 SFR (SFR address = 80H). Port 0 pins
that have 1s written to them via the Port 0 SFR will be configured
as open-drain and will therefore float. In that state, Port 0 pins can
be used as high impedance inputs. An external pull-up resistor
will be required on Port 0 outputs to force a valid logic high
level externally. 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 pull-ups when emitting 1s.
Port 1 is also an 8-bit port directly controlled via the P1 SFR
(SFR address = 90H). Port 1 is an input only port. Port 1 digital
output capability is not supported on this device. Port 1 pins can
be configured as digital inputs or analog inputs.
By (power-on) default these pins are configured as analog inputs,
i.e., “1” written in the corresponding Port 1 register bit. To
configure any of these pins as digital inputs, the user should write
a “0” to these port bits to configure the corresponding pin as a
high impedance digital input.
These pins also have various secondary functions described in
Table XIII.
Pin
P1.0
P1.1
P1.5
Port 2 is a bidirectional port with internal pull-up resistors directly
controlled via the P2 SFR (SFR address = A0H). Port 2 pins
that have 1s written to them are pulled high by the internal pull-up
resistors and, in that state, can be used as inputs. As inputs, Port
2 pins being pulled externally low will source current because of
the internal pull-up resistors. Port 2 emits the high order
address bytes during fetches from external program memory,
and middle and high order address bytes during accesses to the
24-bit external data memory space.
REV. E
Table XIII. Port 1, Alternate Pin Functions
Alternate Function
T2 (Timer/Counter 2 External Input)
T2EX (Timer/Counter 2 Capture/Reload Trigger)
SS (Slave Select for the SPI Interface)
–29–
Port 3 is a bidirectional port with internal pull-ups directly
controlled via the P3 SFR (SFR address = B0H). Port 3 pins
that have 1s written to them are pulled high by the internal pull-ups
and, in that state, can be used as inputs. As inputs, Port 3 pins
being pulled externally low will source current because of the internal
pull-ups. Port 3 pins also have various secondary functions
described in Table XIV.
Pin
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
The alternate functions of P1.0, P1.1, P1.5, and Port 3 pins
can be activated only if the corresponding bit latch in the P1
and P3 SFRs contains a 1. Otherwise, the port pin is stuck at 0.
Timers/Counters
The ADuC812 has three 16-bit Timer/Counters: Timer 0,
Timer 1, and Timer 2. The Timer/Counter hardware has been
included on-chip to relieve the processor core of the overhead
inherent in implementing timer/counter functionality in software.
Each Timer/Counter consists of two 8-bit registers, THx and
TLx (x = 0, 1, and 2). All three can be configured to operate
either as timers or event counters.
In Timer function, the TLx register is incremented every machine
cycle. Thus, think of it as counting machine cycles. Since a
machine cycle consists of 12 core clock periods, the maximum
count rate is 1/12 of the core clock frequency.
In Counter function, the TLx register is incremented by a 1-to-0
transition at its corresponding external input pin, T0, T1, or T2.
In this function, the external input is sampled during S5P2 of
every machine cycle. When the samples show a high in one cycle and
a low in the next cycle, the count is incremented. The new count
value appears in the register during S3P1 of the cycle following the
one in which the transition was detected. Since it takes two machine
cycles (24 core clock periods) to recognize a 1-to-0 transition,
the maximum count rate is 1/24 of the core clock frequency.
There are no restrictions on the duty cycle of the external input
signal, but to ensure that a given level is sampled at least once
before it changes, it must be held for a minimum of one full
machine cycle.
Table XIV. Port 3, Alternate Pin Functions
Alternate Function
RxD (UART Input Pin)
(or Serial Data I/O in Mode 0)
TxD (UART Output Pin)
(or Serial Clock Output in Mode 0)
INT0 (External Interrupt 0)
INT1 (External Interrupt 1)
T0 (Timer/Counter 0 External Input)
T1 (Timer/Counter 1 External Input)
WR (External Data Memory Write Strobe)
RD (External Data Memory Read Strobe)
ADuC812