TS68230CFN8 データシートの表示（PDF） - STMicroelectronics

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TS68230CFN8

HMOS PARALLEL INTERFACE/TIMER

STMicroelectronics 

TS68230

SECTION 1

INTRODUCTION

The TS68230 parallel interface/timer (PI/T) provides

versatile double buffered parallel interfaces and a

system oriented timer for TS68000 systems. The

parallel interfaces operate in unidirectional or bidi-

rectional modes, either 8 or 16 bits wide. In the uni-

directional modes, an associated data direction

register determines whether each port pin is an input

or output. In the bidirectional modes the data direc-

tion registers are ignored and the direction is deter-

mined dynamically by the state of four handshake

pins. These programmable handshake pins provide

an interface flexible enough for connection to a wide

variety of low, medium, or high speed peripherals or

other computer systems. The PI/T ports allow use

of vectored or autovectored interrupts, and also pro-

vide a DMA request pin for connection to the 68440

direct memory access controller (DMAC) or a similar

circuit. The PI/T timer contains a 24-bit wide counter

and a 5-bit prescaler. The timer may be clocked by

the system clock (PI/T CLK pin) or by an external

clock (TIN pin), and a 5-bit prescaler can be used.

It can generate periodic interrupts, a square wave,

or a single interrupt after a programmed time period.

It can also be used for elapsed time measurement

or as a device watchdog.

..Features of the PI/T include :

TS68000 Bus Compatible

Port Modes Include :

Bit I/O

Unidirectional 8 Bit and 16 Bit

Bidirectional 8 Bit and 16 Bit

. Programmable Handshaking Options

. 24-Bit Programmable Timer Modes

. Five Separate Interrupt Vectors

. Separate Port and Timer Interrupt Service

Requests

. Registers are Read/Write and Directly

Addressable

. Registers are Addressed for MOVEP (Move

Peripheral) and DMAC Compatibility

The PI/T consists of two logically independent sec-

tions : the ports and the timer. The port section

consists of port A (PA0-PA7), port B (PB0-PB7), four

handshake pins (H1, H2, H3, and H4), two general

input/output (I/O) pins, and six dual-function pins.

The dual-function pins can individually operate as a

third port (port C) or an alternate function related to

either port A, port B, or the timer. The four program-

mable handshake pins, depending on the mode,

can control data transfer to and from the ports, or

can be used as interrupt generating inputs or I/O

pins. Refer to figure 1.1.

The timer consists of a 24-bit counter, optionally

clocked by a 5-bit prescaler. Three pins provide

complete timer I/O : PC2/TIN, PC3/TOUT, and

PC7/TIACK. Only the ones needed for the given

configuration perform the timer function, while the o-

thers remain port C I/O.

The system bus interface provides for asynchro-

nous transfer of data from the PI/T to a bus master

over the data bus (D0-D7). Data transfer acknow-

ledge (DTACK), register selects (RS1-RS5), timer

interrupt acknowledge (TIACK), read/write line

(R/W), chip select (CS), or port interrupt acknow-

ledge (PIACK) control data transfer between the

PI/T and an TS68000.

1.1. PORT MODE DESCRIPTION

The primary focus of most applications will be on

port A, port B, the handshake pins, the port interrupt

pins, and the DMA request pin. They are controlled

in the following way : the port general control register

contains a 2-bit field that specifies one of four ope-

ration modes. These govern the overall operation of

the ports and determine their interrelation-ships.

Some modes require additional information from

each port’s control register to further define its ope-

ration. In each port control register, there is a 2-bit

submode field that serves this purpose. Each port

mode/submode combination specifies a set of pro-

grammable characteristics that fully define the be-

havior of that port and two of the handshake pins.

This structure is summarized in table 1.1 and fig-

ure 1.2.

2/61

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