LED Pulse Generator
7-101
MPU Public Peripherals
7.9.2
LPG Design
LCR bit 6 = 0 resets the whole pulse generator circuit (but not the control regis-
ter) and switches off the LED. It is possible to switch on the LED independently
from the pulse generator circuit with bit 7 of the LCR (1 = permanent light). A
device reset causes a reset to the whole LPG (with the control register) and
the output LPG_LED to zero asynchronously.
Because the TIPB write to the LPG control register is asynchronous, the value
written to the control register may be unstable for one blink period. Conse-
quently, the LED output could, in the worst case, be switched on at maximum
intensity during one additional blink period.
7.9.3
LPG Power Management
The LPG input clock comes from the 32-kHz ULPD clock, because it must work
even when the OMAP5910 system is in deep sleep mode. The internal clock
of the LPG runs with 256 Hz. For this reason the power consumption of this
block can be neglected. Nevertheless, switch the LPG_CLK off if LPG is not
used.
7.9.4
LPG Registers
Both receive and transmit registers are mapped in the MPU address space.
Two instances of LPG are mapped in the OMAP5910 device:
-
First LPG: LPG_1 address is FFFB:D000
-
Second LPG: LPG_2 address is FFFB:D800
Table 7–73 lists the LPG receive and transmit registers. Table 7–74 and
Table 7–77 describe the register bits.
Table 7–73. LED Pulse Generator Receive and Transmit Registers
Register
Description
Access
Field Size
Offset (hex)
LCR
LPG control
R/W
8 bits
0x00
PMR
Power management
R/W
8 bits
0x04