DS2172

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2.0 PARALLEL CONTROL INTERFACE

The DS2172 is controlled via a multiplexed bi-directional address/data bus by an external microcontroller

or microprocessor. The DS2172 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 parenthesis (). See the timing diagrams in the A.C. Electrical

Characteristics for more details. The multiplexed bus on the DS2172 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 DS2172 latches

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

also be easily connected to non-multiplexed buses. RCLK and TCLK are used to update counters and

load transmit and receive pattern registers. At slow clock rates, sufficient time must be allowed for these

port operations.

3.0 PATTERN SET REGISTERS

The Pattern Set Registers (PSR) are loaded each time a new pattern (whether it be pseudorandom or

repetitive) is to be generated. When a pseudorandom pattern is generated, all four PSRs must be loaded

with FF Hex. When a repetitive pattern is to be created, the four PSRs are loaded with the pattern that is

to be repeated. Please see Tables 4 and 5 for some programming examples.

PATTERN SET REGISTERS

(MSB)

(LSB)

PS31

PS30

PS29

PS28

PS27

PS26

PS25

PS24

PSR3 (addr.=00 Hex)

PS23

PS22

PS21

PS20

PS19

PS18

PS17

PS16

PSR2 (addr.=01 Hex)

PS15

PS14

PS13

PS12

PS11

PS10

PS9

PS8

PSR1 (addr.=02 Hex)

PS7

PS6

PS5

PS4

PS3

PS2

PS1

PS0

PSR0 (addr.=03 Hex)

4.0 PATTERN LENGTH REGISTER

Length Bits LB4 to LB0 determine the length of the pseudorandom polynomial or programmable

repetitive pattern that is generated and detected. With the pseudorandom patterns, the “Tap A” feedback

position of the pattern generator is always equal to the value in the Pattern Length Register (PLR). Please

refer to Figure 2 for a block diagram of the pattern generator and to Tables 4 and 5 for some

programming examples.