HI-7159A Datasheet PDF

HI-7159A View Datasheet(PDF) - Intersil

Part Name

Description

Manufacturer

HI-7159A

Microprocessor-Compatible, 5-1/2 Digit A/D Converter

Intersil

HI-7159A Datasheet PDF : 14 Pages

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HI-7159A

Serial Mode 2

Serial Mode 2 is selected by tying SEL (pin 28) low, SMS0

(pin 18) high, and SMS1 (pin 19) low, as shown in Figure 4C.

This mode of operation is identical to Serial Mode 1, except

that each device now has one of 32 unique addresses

determined by the state of pins 20-23 and 17, as shown in

Table 3. This allows multiple HI-7159As to be attached to the

same pair of serial lines.

When the microprocessor sends out an Address Byte (Table

4) that matches one of the HI-7159As’ hardwired addresses,

that particular HI-7159A is selected for all further I/O until

another Address Byte with a different address is

transmitted.

TABLE 3. HARDWARE ADDRESS SELECTION FOR MODE 2

PIN 17

PIN 23

PIN 22

PIN 21

PIN 20

B4 (MSB)

B0 (LSB)

Reading the HI-7159A

Despite the wide variety of interface options available on the

HI-7159A, the procedure for communicating with it is

essentially the same in all four modes. (Serial Mode 2 differs

from the rest in two respects: the chip to be communicated

with must ﬁrst be sent an address byte to select it, and the

digit bytes are sent one by one, for a total of six bytes,

instead of in pairs.) There are two types of bytes that can be

sent to the converter, commands and requests. A command

byte (Table 5) sets the parameters of and initiates a

conversion. Those parameters are: continuity of the

conversion (single or continuous), resolution (51/2 or 41/2

digits), and type of conversion (Compensated,

Uncompensated, or Error Only). Bit D0 = 0 indicates that this

is a command byte and a new conversion(s) should be

started.

A request byte (Table 6) asks for either the status of the

converter or the result of a conversion. All bits of a request

should be set to 0 except D3, D2, and D0. D3 and D2

determine the type of request (status or digit pair), and D0 =

1 indicates to the HI-7159A that this is a request byte. Serial

Mode 2 uses a slightly modiﬁed request byte, shown in Table

7, allowing it to individually select each of the six digit bytes.

Upon receipt of a request, the HI-7159A will respond with

either a status or a digit byte. The status byte (Table 8)

returns the current state of the converter. Bit D6 = 1

indicates that a new conversion has been completed since

the last time the status byte was read. Bit D6 is cleared after

it is read. Bit D4 shows the current continuity (single or

continuous). Bit D3 indicates the resolution (51/2 or 41/2

digits) of the conversion, and bits D2 and D1 indicate the

type (Compensated, Uncompensated, or Error Only). Bit

D0 = 0 indicates that there was no parity error detected in

the last request byte.

The three digit bytes (Table 9) each contain two nibbles

representing two digits of the conversion. The sixth nibble

contains the MSD (most signiﬁcant digit), polarity

(1 = positive) and overrange (1 = overrange) information. In

Serial Mode 2 the digits (Table 10) are requested and

received individually, so a total of six requests and six reads

is necessary to obtain all 51/2 digits.

ADDRESS BIT

TABLE 4. SERIAL MODE 2 ADDRESS BYTE FORMAT (SENT TO HI-7159A)

(RESERVED)

(MSB)

(LSB)

(RESERVED)

TABLE 5. COMMAND BYTE FORMAT (SENT TO HI-7159A)

CONTINUITY

RESOLUTION

CONVERSION TYPE

Single

Continuous

0 51/2

1 41/2

1 Comp

0 Uncomp

Error Only

COMMAND BIT

TABLE 6. REQUEST BYTE FORMAT, PARALLEL AND SERIAL MODE 1 (SENT TO HI-7159A)

(RESERVED)

BYTE REQUEST

(RESERVED)

REQUEST BIT

Digit Pair 0, 1

Digit Pair 2, 3

Digit Pair 4, 5

Converter Status

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