SCI

The SCI is a full-duplex UART type asynchronous system, using standard non return to zero (NRZ) format : 1 start bit, 8 or 9 data bits and a 1 stop bit. The Core resynchronizes the receiver bit clock on all one to zero transitions in the bit stream. Therefore differences in baud rate between the sending device and the SCI are not as likely to cause reception errors. Three logic samples are taken near the middle of data bit time, and majority logic decides the sense for the bit. For the start and stop bits seven logic samples are taken. Even if noise causes one of these samples to be incorrect, the bit will still be received correctly. The receiver also has the ability to enter a temporary standby mode (called receiver wakeup) to ignore messages intended for a different receiver. Logic automatically wakes up the receiver in time to see the first character of the next message. This wakeup feature greatly reduces CPU overhead in multidrop SCI networks. The SCI transmitter can produce queued characters of idle (whole characters of all logic 1) and break (whole characters of all logic 0). In addition to the usual transmit data register empty (TDRE) status flag, this SCI also provides a transmit complete (TC) indication that can be used in applications with a modem.

SPI

It’s a fully configurable master/slave Serial Peripheral Interface, which allows user to configure polarity and phase of serial clock signal SCK. It allows the microcontroller to communicate with serial peripheral devices. It is also capable of interprocessor communications in a multi-master system. A serial clock line (SCK) synchronizes shifting and sampling of the information on the two independent serial data lines. SPI data are simultaneously transmitted and received. SPI system is flexible enough to interface directly with numerous standard product peripherals from several manufacturers. Data rates as high as CLK/8. Clock control logic allows a selection of clock polarity and a choice of two fundamentally different clocking protocols to accommodate most available synchronous serial peripheral devices. When the SPI is configured as a master, software selects one of four different bit rates for the serial clock. Error-detection logic is included to support interprocessor communications. A write-collision detector indicates when an attempt is made to write data to the serial shift register while a transfer is in progress. A multiple-master mode-fault detector automatically disables SPI output drivers if more than one SPI devices simultaneously attempts to become bus master.

I/O Ports

General Purpose I/O Ports, when enabled the I/O Ports are shared with particular on chip peripherals: SCI, SPI, TIMER.

PULSEACCA

This system is based on an 8-bit counter and can be configured to operate as a simple event counter or for gated time accumulation. Unlike the main timer, the 8-bit pulse accumulator counter can be read or written at any time (the 16-bit counter in the main timer cannot be written). Control bits allow the user to configure and control the pulse accumulator subsystem. Two maskable interrupts are associated with the system, each having its own controls and interrupt vector. The PAI pin associated with the pulse accumulator can be configured to act as a clock (event counting mode) or as a gate signal to enable a free-running E divided by 64 clock to the 8-bit counter (gated time accumulation mode). The alternate functions of the pulse accumulator input (PAI) pin present some interesting application possibilities.

BUSCTRL

Bus Controller - manages data exchange between CPU and seweral Internal and External Memories

COP

COP Watchdog Timer

CTRLUNIT

It performs the core synchronization and data flow control. This module manages execution of all instructions.

Interrupt Controller

D68HC11 has implemented 17-level interrupt priority control. External interrupt pins are activated at low level(XIRQ,IRQ pins) or falling edge (IRQ pin). External interrupt requests by IRQ, XIRQ are sampled each 1 system clock at the rising edge of CLK. The D68HC11 peripheral systems generate maskable interrupts, which are recognized only if the global interrupt mask bit (I) in the CCR is cleared. Maskable interrupts are prioritized according to default arrangement (look at the table below) established during reset. However any one source may be elevated to the highest maskable priority position using HPRIO register. When interrupt condition occurs, an interrupt status flag is set to indicate the condition.

TIMER

Main Timer system, including Compare, Capture and Real Time Interrupt logic. This timer system is based on a free-running 16-bit counter with a 4-stage programmable prescaler. A timer overflow function allows software to extend the timing capability of the system beyond the 16-bit range of the counter. Three independent input-capture functions are used to automatically record the time when a selected transition is detected at a respective timer input pin. Five output-compare functions are included for generating output signals or for timing software delays. Since the input-capture and output-compare functions may not be familiar to all users, these concepts are explained in greater detail.
A programmable periodic interrupt circuit called RTI is tapped off of the main 16-bit timer counter. Software can select one of four rates for the RTI, which is most commonly used to pace the execution of software routines. The COP watchdog function is closely related to the main timer in that the clock input to the COP system (clk*2^17) is tapped off the free-running counter chain.
The timer subsystem involves more registers and control bits than any other subsystem on the MCU. Each of the three input-capture func-tions has its own 16-bit time capture latch (input-capture register) and each of the five output-compare functions has its own 16-bit compare register. All timer functions, including the timer overflow and RTI, have their own interrupt controls and separate interrupt vectors. Additional control bits permit software to control the edge(s) that trigger each input-capture function and the automatic actions that result from output-compare functions. Although hardwired logic is included to automate many timer activities, this timer architecture is essentially a software-oriented system. This structure is easily adaptable to a very wide range of applications although it is not as efficient as dedicated hardware for some specific timing applications.

ADCCTRL

External ADC Controller. Allows to control external ADC's with standart HC11 ADC software. Supports several Parallel and serial ADC's.

DoCD^TM

DoCD^TM Debug Unit – it’s a real-time hardware debugger provides debugging capability of a whole SoC system. In contrast to other on-chip debuggers DoCD™ provides non-intrusive debugging of running application. It can halt, run, step into or skip an instruction, read/write any contents of microcontroller including all registers, internal, external, program memories, all SFRs including user defined peripherals. Hardware breakpoints can be set and controlled on program memory, internal and external data memories, as well as on SFRs. Hardware breakpoint is executed if any write/read occurred at particular address with certain data pattern or without pattern. The DoCD^TM system includes three-wire interface and complete set of tools to communicate and work with core in real time debugging. It is built as scalable unit and some features can be turned off to save silicon and reduce power consumption. A special care on power consumption has been taken, and when debugger is not used it is automatically switched in power save mode. Finally whole debugger is turned off when debug option is no longer used.
The separate DoCD^TM clock line allow debugger to operate while the SLEEP mode (major clock line CLK is stopped).

ALU

Arithmetic Logic Unit performs the arithmetic and logic operations during execution of an instruction. It contains accumulator (A, B), Condition Code Register (CCREG), and related logic such as arithmetic unit, logic unit, multiplier and divider.

Performance

D68HC11 implementation results for ACTEL devices. All features have been included.