8-4
MSM66573 Family User's Manual
Chapter 8 General-Purpose 8/16 Bit Timers
8.4.2 Description of Timer 0 Registers
(1)
General-purpose 16-bit timer 0 counter (TM0C)
The general-purpose 16-bit timer 0 counter (TM0C) is a 16-bit up-counter. When this
counter overflows, an interrupt request is generated and it is loaded with the contents of
general-purpose 16-bit timer 0 register (TM0R).
TM0C can be read from and written to by the program.
When reset (
RES signal input, execution of a BRK instruction, overflow of the watchdog
timer, opcode trap), the contents of TM0C are undefined.
[Note]
Writing a timer value to TM0C causes the same value to also be written to the general-
purpose 16-bit timer 0 register (TM0R).
(2)
General-purpose 16-bit timer 0 register (TM0R)
The general-purpose 16-bit timer 0 register (TM0R) consists of 16 bits. This register stores
the value to be reloaded into the general-purpose 16-bit timer 0 counter (TM0C).
TM0R can be read from and written to by the program.
When reset (
RES signal input, execution of a BRK instruction, overflow of the watchdog
timer, opcode trap), the contents of TM0R are undefined.
(3)
General-purpose 16-bit timer 0 control register (TM0CON)
The general-purpose 16-bit timer 0 control register (TM0CON) consists of 5 bits. Bits 0 to
2 (TM0C0 to TM0C2) of TM0CON select the timer 0 count clock, bit 3 (TM0RUN) starts or
halts the counting, and bit 7 (TM0OUT) specifies the initial timer output level (High or Low)
at start-up.And each time TM0C overflows, the content of bit 7 (TM0OUT) is reversed.
TM0CON can be read from and written to by the program. However, write operations are
invalid for bits 4 to 6. If read, a value of "1" will always be obtained for bits 4 to 6.
When reset (
RES signal input, execution of a BRK instruction, overflow of the watchdog
timer, opcode trap), TM0CON becomes 70H.
Figure 8-2 shows the TM0CON configuration.
[Note]
Just before TM0C overflows, if an SB, RB, XORB or other read-modify-write instruction
is performed on TM0CON, then TM0OUT may not operate correctly.