HI-7159A Просмотр технического описания (PDF) - Renesas Electronics
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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)
B3
B2
B1
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.
TABLE 4. SERIAL MODE 2 ADDRESS BYTE FORMAT (SENT TO HI-7159A)
ADDRESS BIT
(RESERVED)
(MSB)
(LSB)
D7
D6
D5
D4
D3
D2
D1
D0
1
0
0
B4
B3
B2
B1
B0
(RESERVED)
D7
D6
D5
0
0
0
TABLE 5. COMMAND BYTE FORMAT (SENT TO HI-7159A)
CONTINUITY
RESOLUTION
CONVERSION TYPE
Single
Continuous
D4
0 51/2
1 41/2
D3
1 Comp
0 Uncomp
Error Only
D2
D1
1
1
1
0
0
1
COMMAND BIT
D0
0
TABLE 6. REQUEST BYTE FORMAT, PARALLEL AND SERIAL MODE 1 (SENT TO HI-7159A)
(RESERVED)
BYTE REQUEST
(RESERVED)
REQUEST BIT
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
Digit Pair 0, 1
0
0
0
1
Digit Pair 2, 3
0
1
Digit Pair 4, 5
1
0
Converter Status
1
1
FN2936 Rev 4.00
January 1999
Page 8 of 14
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