Global Mixed-mode Technology Inc.
G781
Command Byte Functions
Status Byte Functions
The 8-bit command byte register (Table 5) is the mas-
ter index that points to the various other registers
within the G781. 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 status byte register (Table 7) indicates 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 DXP-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 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 auto-
matic conversion takes place after a full delay elapses.
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 configura-
tion byte). In one-shot mode, read the status byte only
after the conversion is complete, which is approxi-
mately 125ms max after the one-shot conversion is
commanded.
Configuration Byte Functions
The configuration byte register (Table 6) is used to
mask interrupts and to put the device in software
standby mode. The other bits are empty.
Table 5. Command-Byte Bit Assignments
REGISTER
RLTS
COMMAND
00h
POR STATE
0000 0000*
0000 0000*
N/A
FUNCTINON
Read local temperature. It returns latest temperature
Read remote temperature. It returns latest temperature
Read status byte (flags, busy signal)
Read configuration byte
RRTE
RSL
RCL
01h
02h
03h
0000 0000
RCRA
04h
0000 1000
Read conversion rate byte
RLHN
RLLI
RRHI
05h
06h
07h
0101 0101 (85) Read local THIGH limit
0000 0000 Read local TLOW limit
0101 0101 (85) Read remote THIGH limit
RRLS
08h
0000 0000
Read remote TLOW limit
WCA
09h
N/A
Write configuration byte
WCRW
WLHO
WLLM
WRHA
WRLN
OSHT
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
19h
20h
21h
22h
FEh
FFh
N/A
N/A
N/A
N/A
N/A
N/A
0
0
Write conversion rate byte
Write local THIGH limit
Write local TLOW limit
Write remote THIGH limit
Write remote TLOW limit
One-shot command (use send-byte format)
Remote temperature extended byte
Remote temperature offset high byte
Remote temperature offset extended byte
Remote THIGH limit extended byte
Remote TLOW limit extended byte
Remote temperature THERM limit
Local temperature THERM limit
THERM hysteresis
RTEXT
RTOFS
RTOFSEXT
RLEXT
RHEXT
RTTHERM
LTTHERM
THERMHYST
ALERTFQ
MFGIO
DEVID
0
0
0
0101 0101 (85)
0101 0101 (85)
0000 1010 (10)
0
0100 0111
0000 0001
ALERT fault queue code
Manufacturer ID
Device ID
*If the device is in standby mode at POR, both temperature registers read 0°C.
Ver: 1.0
Oct 02, 2002
10
TEL: 886-3-5788833
http://www.gmt.com.tw
ETC [ ETC ]
