MIC184 Micrel Semiconductor, MIC184 Datasheet - Page 15

• Manufacturer Part Number: MIC184
• Description: Local/Remote Thermal Supervisor Advance Information
• Manufacturer: Micrel Semiconductor

Applications Information
Switching Zones
The recommended procedure for switching between the
internal and external zones is as follows:
At the conclusion of the serial bus transaction for step 4, the
A/D converter will begin a conversion cycle using the new
zone setting. The next conversion cycle completed after the
serial bus transaction for step 5 will result in the state of the
INT output being updated (if enabled) for the new zone.
Generally the MIC184’s A/D converter operates continu-
ously, but it will be halted and reset each time the part
recognizes its slave address on the serial bus. Interrupted
conversions will remain halted until the end of the host’s
communication with the MIC184. After the completion of step
5 and a delay of t
contain the results for the new zone. The above routine is
extremely unlikely to miss a temperature event, as even one
A/D conversion is typically much slower than the I
transactions that control the MIC184. See Figure 6: A/D
Converter Timing.
Step 2(c) is recommended because the MIC184 has only one
CONFIG register, corresponding to the active zone. In order
to preserve data integrity for both zones, 2(c) allows the host
to create a virtual CONFIG register for the inactive zone by
dedicating one byte of memory to that purpose. Additional
virtual registers may be created as needed by inserting
additional reads as steps 2(d), 2(e), etc. These could for
example correspond to the values in T_SET and T_HYST
immediately prior to switching zones. Steps 4(b) and 5
ensure that the MIC184 will enter the new zone searching for
an overtemperature event.
November 2000
MIC184
1. Disable interrupts (if used)
2. Read the CONFIG register to:
3. Write the appropriate values to
4. Write to CONFIG as follows:
5. If interrupts are being used, MODE must then be
by setting the IM bit in CONFIG.
a) Verify no masked interrupt was pending
b) Clear STS prior to switching zones
c) Hold the settings of CONFIG register for the
T_SET and T_HYST for the new zone.
a) To toggle the ZONE bit (1 = remote, 0 =
b) If interrupts are being used, step 4 should
set to 1 and IM reset to 0
(D[7] = 0)
current zone
internal)
also clear MODE
CONV
x Fault_Queue , STS and INT will
2
C/SMBus
15
Identifying an MIC184 by Software Test
{START Interrupt-Driven Test and Initialization
1. Disable the host’s overtemperature and
2. Write 0000 0010b (02h) to the CONFIG register.
3. Write 1100 1000 1000 0000b = C880h to T_SET
4. When the part has finished its first A/D conver-
5. Read out the contents of the CONFIG register:
6.Write 0111 1111 1000 0000b = 7F80h to T_SET
7.When the part has finished its next A/D conver-
8.Read CONFIG again, to clear the interrupt
9.Based on the results of the test in step (4), do the
{END}
Routine}
undertemperature interrupt handling routine.
Redirect interrupts from the part under test to a
handler for the interrupt that will be generated in
steps (4) and (7) of this routine.
(The assumption is made that the host is an I
or SMBus part, and therefore responds to an
active-low interrupt request.)
and T_HYST. This corresponds to -55.5 C.
sion, INT will be asserted.
a) If the part is an MIC184, the MSB will be set
b) If the part is a conventional LM75-type part,
and T_HYST. This corresponds to +127.5 C.
sion, INT will be asserted a second time.
request from step (7). This will also clear STS, if
the part under test is an MIC184.
following within 50ms total:
a) Set the CONFIG register as required.
b) Load T_HYST with its operational value.
c) Load T_SET with its operational value.
d) Set the host’s interrupt handling routine back
to one (CONFIG = 1000 0010b = 82h).
the MSB will be zero (CONFIG = 0000
0010b = 02h).
to overtemperature and undertemperature
mode.
MIC184
2
C
Micrel