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C005383_10 CR80XX Integration Guide
11 – APPENDIX B: Optimizing for Low Power Applications
Register
0x9F
controls the duration between a completed read operation
and when the unit goes to sleep. It should be written with a small,
non-zero value to minimize the idle time between scan completion
and the CR8000 entering sleep mode.
The host needs to assert the
nWakeUp
pin and wait for the PwrDwn pin
to be negated before the host can communicate with the CR8000. By
programming register
0x9F
and performing this operation, the time that the
CR8000 remains awake can be minimized.
Long-Term Communication
The following timing diagram shows the general
process for waking up and communicating with
the CR8000 on a long-term basis. This includes
configuration and performing firmware upgrades
on the engine. Please refer to Section 12.3 for all
appropriate timing values.
1. Host asserts
nWakeUp
for at least
T
wupw
, and is optionally held low until
communication with the CR8000 is finished
2. After
T
wu
, CR8000 negates
PwrDwn
3. After
T
cmddelay
, host writes register
0x9F
with 0x80000000 to disable sleep timer
4. Host communicates with CR8000
5. Host writes register
0x9F
with appropriate
value to enable sleep timer
Note: There are several timeouts the CR8000
uses for various modes. To fine tune the total
timeout of Idle and Sleep modes, reference
registers 0x9F, 0x2C, and 0x32 in the ICD.
11.1 – Configuration
11.2 – Communications from Sleep Mode
Achieving low power consumption with the CR8000 requires that certain
setup and configuration values be programmed into the Scan Engine, as
well as certain protocols that need to be followed to wake up from sleep
mode. This appendix describes these operations.
This applies to the
RS232 interface model only.
Wake-Up Communication Timing Diagram
T
WUPW
nWakeUp
T
CMDDELAY
T
SU
T
WU
PwrDwn
Data
DATA
WR REG 0X9F
WR REG 0X9F
