ST75C540 datasheet(6/84 Pages) STMICROELECTRONICS

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II.2 - Host Interface

The exchanges with the control processor proceed through a 128 x 8 DUAL port RAM shared between the

ST75C530/540 and the Host. The signals associated with this interface are :

Pin Name

Type

Description

SD0..SD7

I/O

System Data Bus. 8-bit data bus used for asynchronous exchanges between t he

ST75C530/540 and the Host through the dual port RAM. High impedance when exchanges

are not active.

SA0..SA6

System Address Bus. 7-bit address bus for dual port RAM, IO and interrupt registers.

SDS (SRD)

System Data Strobe. In Motorola mode SDS initiates the exchange, active low. In Intel mode

SRD initiates a read exchange, active low.

SR/W (SWR)

System Read/Write. In Motorola mode SR/W defines the type of exchange read/write. In Intel

mode SWR initiates a write exchange, active low.

SCS

System Chip Select. Active low.

SINTR

System Interrupt Request. Open drain. Active low. This signal isasserted by the ST75C530/540

and negated by the host.

RESET

Reset. Active low.

INT/MOT

Select Intel or Motorola Interface

II.3 - Analog Interface

Pin Name

Type

Description

TxA1

Transmit Analog Output 1

TxA2

Transmit Analog Output 2

RxA

Receive Analog Input

SPK1P

Speaker Output 1, (differential positive), must be connected through Amplifier to the

loudspeaker.

SPK1N

Speaker Output 1, (differential negative)

SPK2P

Speaker Output 2, (differential positive), must be connected through Amplifier to the Handset

loudspeaker.

SPK2N

Speaker Output 2, (differential negative)

SPK3P

Speaker Output 3, (differential positive)

SPK3N

Speaker Output 3, (differential negative)

MIC1

Microphone Input 1

MIC2

Microphone Input 2

MIC3

Microphone Input 3

VCM

I/O

Analog Common Voltage (nominal +2.5V). This input must be decoupled with respect to AGND.

VREFN

Analog Negative Reference (nominal 1.25V). This input must be decoupled with respect to

VCM.

VREFP

Analog Positive Reference (nominal 3.75V). This input must be decoupled with respect to VCM.

II.4 - General Purpose IO and Relay

Pin Name

Type

Description

GIO[0,7]

I/O

General Purpose I/O Pins, can be independently selected as input or output.

GIO[10,17]

I/O

General Purpose I/O Pins, can be independently selected as input or output.

RELAY0,

RELAY1

Relay Outputs, Open Drain, Active Low. Can sink -10mA to RGND.

RING

Ring detect signal. Active low. If the ST75C530/540 is in low power mode, a low level will awake

the chip. This input is a Schmidt’s trigger.

RGND

PWR

Relay Digital Ground. To connect to GND.

II - PIN DESCRIPTION (continued)

ST75C530 - ST75C540

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