DS2143 datasheet(8/44 Pages) DALLAS

8 / 44 page

DS2143/DS2143Q

8 of 44

ADDRESS

A7 to A0

HEX

R/W

NAME

01001101

R/W

Transmit

Signaling

01001110

R/W

Transmit

Signaling

01001111

R/W

Transmit

Signaling

Note: All values indicated within the Address

column are hexadecimal.

2.0 PARALLEL PORT

The DS2143 is controlled via a multiplexed bidirectional address/data bus by an external microcontroller

or microprocessor. The DS2143 can operate with either Intel or Motorola bus timing configurations. If

the BTS pin is tied low, Intel timing will be selected; if tied high, Motorola timing will be selected. All

Motorola bus signals are listed in parentheses (). See the timing diagrams in the AC Electrical

Characteristics for more details. The multiplexed bus on the DS2143 saves pins because the address

information and data information share the same signal paths. The addresses are presented to the pins in

the first portion of the bus cycle and data will be transferred on the pins during second portion of the bus

cycle. Addresses must be valid prior to the falling edge of ALE(AS), at which time the DS2143 latches

the address from the AD0 to AD7 pins. Valid write data must be present and held stable during the later

portion of the DS or WR pulses. In a read cycle, the DS2143 outputs a byte of data during the latter

portion of the DS or RD pulses. The read cycle is terminated and the bus returns to a high impedance

state as RD transitions high in Intel timing or as DS transitions low in Motorola timing.

3.0 CONTROL AND TEST REGISTERS

The operation of the DS2143 is configured via a set of five registers. Typically, the control registers are

only accessed when the system is first powered up. Once the DS2143 has been initialized, the control

registers will only need to be accessed when there is a change in the system configuration. There are two

Receive Control Registers (RCR1 and RCR2), two Transmit Control Registers (TCR1 and TCR2), and a

Common Control Register (CCR). Each of the five registers is described in this section.

The Test Register at address 15 hex is used by the factory in testing the DS2143. On power-up, the Test

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