LM3S1138 Luminary Micro, Inc, LM3S1138 Datasheet - Page 41

• Manufacturer Part Number: LM3S1138
• Description: Lm3s1138 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

July 26, 2008
of 0 is possible, but has no effect because the SysTick interrupt and COUNTFLAG are activated
when counting from 1 to 0.
Therefore, as a multi-shot timer, repeated over and over, it fires every N+1 clock pulse, where N is
any value from 1 to 0x00FF.FFFF. So, if the tick interrupt is required every 100 clock pulses, 99
must be written into the RELOAD. If a new value is written on each tick interrupt, so treated as single
shot, then the actual count down must be written. For example, if a tick is next required after 400
clock pulses, 400 must be written into the RELOAD.
SysTick Current Value Register
Use the SysTick Current Value Register to find the current value in the register.
SysTick Calibration Value Register
The SysTick Calibration Value register is not implemented.
Bit/Field
Bit/Field
31:24
31:24
23:0
23:0
RELOAD
CURRENT
reserved
reserved
Name
Name
Type
W1C
RO
Type
W1C
RO
Reset
Reset
0
-
0
-
Description
Software should not rely on the value of a reserved bit. To provide compatibility with
future products, the value of a reserved bit should be preserved across a read-modify-write
operation.
Reload
Value to load into the SysTick Current Value Register when the counter reaches 0.
Description
Software should not rely on the value of a reserved bit. To provide compatibility with
future products, the value of a reserved bit should be preserved across a
read-modify-write operation.
Current Value
Current value at the time the register is accessed. No read-modify-write protection is
provided, so change with care.
This register is write-clear. Writing to it with any value clears the register to 0. Clearing
this register also clears the COUNTFLAG bit of the SysTick Control and Status Register.
Preliminary
LM3S1138 Microcontroller
41