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G768 View Datasheet(PDF) - Unspecified

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G768 Datasheet PDF : 15 Pages
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Global Mixed-mode Technology Inc.
G768B
Command Byte Functions
The 8-bit command byte register (Table 4) is the mas-
ter index that points to the various other registers
within the G768B. The register's POR state is 0000
0000, so that a Receive Byte transmission (a protocol
that lacks the command byte) that occurs immediately
after POR returns the current local temperature data.
The one-shot command immediately forces a new
conversion cycle to begin. In software standby mode
( RUN /STOP bit = high), a new conversion is begun,
after which the device returns to standby mode. If a
conversion is in progress when a one-shot command
is received in auto-convert mode (RUN/STOP bit = low)
between conversions, a new conversion begins, the
conversion rate timer is reset, and the next automatic
conversion takes place after a full delay elapses.
Thermal Configuration Byte Functions
The configuration byte register (Table 5) is used to
mask (disable) interrupts and to put the device in
software standby mode. The lower six bits are inter-
nally set to (XX1111), making them "don't care" bits.
Write
zeros to these bits. This register's contents can be
read back over the serial interface.
Thermal Status Byte Functions
The thermal status byte register (02h) (Table 6) indi-
cates which (if any) temperature thresholds have been
exceeded. This byte also indicates whether or not the
ADC is converting and whether there is an open circuit
in the remote diode DXPx-DXN path. After POR, the
normal state of all the flag bits is zero, assuming none
of the alarm conditions are present. The status byte is
cleared by any successful read of the status, unless
the fault persists. Note that the ALERT interrupt latch
is not automatically cleared when the status flag bit is
cleared.
When reading the status byte, you must check for in-
ternal bus collisions caused by asynchronous ADC
timing, or else disable the ADC prior to reading the
status byte (via the RUN/STOP bit in the configuration
byte). In one-shot mode, read the status byte only af-
ter the conversion is complete, which is 150ms max
after the one-shot conversion is commanded.
Table 5. Configuration-Byte Bit Assignments
BIT
NAME POR STATE
FUNCTION
7 (MSB) MASK
0
Masks all ALERT interrupts when high.
6 RUN / STOP
0
Standby mode control bit. If high, the device immediately stops converting and enters
standby mode. If low, the device converts in either one-shot or timer mode.
5-0
RFU
0
Reserved for future use
Table 6. Status-Byte Bit Assignments
BIT
NAME
FUNCTION
7(MSB)
BUSY
A high indicates that the ADC is busy converting.
6
RHIGH2*
A high indicates that the 2nd diode high-temperature alarm has activated.
5
RLOW2*
A high indicates that the 2nd diode low-temperature alarm has activated.
4
RHIGH1*
A high indicates that the 1st diode high-temperature alarm has activated.
3
RLOW1*
A high indicates that the 1st diode low-temperature alarm has activated.
2
OPEN*
A high indicates a remote-diode continuity (open-circuit) fault.
1
RFU
Reserved for future use (returns 0)
0(LSB)
RFU
Reserved for future use (returns 0)
*These flags stay high until cleared by POR, or until the status byte register is read.
Table 7. Conversion-Rate Control Byte
DATA
00h
01h
02h
03h
04h
05h
06h
07h
08h to FFh
CONVERSION
RATE (Hz)
0.0625
0.125
0.25
0.5
1
2
4
8
RFU
Ver: 1.3
Oct 28, 2002
Temperature Sensor Average
Supply Current (ยตA TYP, at Vcc = 5V)
30
33
35
48
70
128
225
425
-
TEL: 886-3-5788833
http://www.gmt.com.tw
12
 

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