EM77950 datasheet(88/102 Pages) EMC

88 / 102 page

EM77950

BB Controller

•

Product Specification (V1.0) 10.09.2007

(This specification is subject to change without further notice)

13 Circuitry of Input and Output Pins

13.1

Introduction

The EM77950 has six parallel ports, namely Port A, Port B, Port C, Port D, Port E and

Port F. There are 40 available I/O pins. A control bit defines the configuration of its

corresponding pin. Refer to Fig. 3.1 for the Pin Assignment.

The I/O registers, from Port A to Port F, are bidirectional tri-state I/O ports. The I/O

ports can be defined as "input" or "output" pins by the I/O control registers (IOCA, IOCB,

IOCD, IOCE and IOCF) under program control. The I/O registers and I/O control

registers are both readable and writable.

14 Timer/Counter System

14.1

Introduction

The EM77950 provides two timer modules: 8-bit TCC (Timer Clock/Counter), and

16-bit FRC (Free Run Counter). The clock sources of TCC come from one of the

instruction cycles and low frequency oscillator (IRC). The clock source of FRC is from

either the instruction cycle or low frequency oscillator (IRC).

14.2

Time Clock Counter (TCC)

An 8-bit counter is available as prescaler for the TCC. The prescaler ratio is

determined by the PS0~PS2 bits. When in TCC mode, the prescaler is cleared each

time an instruction writes to the TCC.

TCC is an 8-bit timer/counter. If the TCC signal source is from the system clock,

TCC will be incremented by 1 for every instruction cycle (without prescaler).

If the TCC signal source is from the IRC clock input, TCC will be incremented by 1

on every falling edge or rising edge of the TCC pin.

The prescaler counter (PRC) can be read from Address 0x0F. In other words, the

combination of TCC and PRC can be used as a 16-bit counter without prescaler

14.2.1

Block Diagram of TCC

PRC (8- bit Counter)

8-1 MUX

TCC

PS0

PS1

PS2

TCCOF

Data Bus

Fosc

IRC

TCCE

Sync with

Internal

Clock

2 clocks delay

TCCS0

Fig. 14-1 Function Block Diagram of TCC

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