CHAPTER 6 16-BIT TIMER
(1) 16-bit compare register 90 (CR90)
A value specified in CR90 is compared with the count in 16-bit timer register 90 (TM90). If they match, an
interrupt request (INTTM90) is issued by CR90.
CR90 is set with an 8-bit or 16-bit memory manipulation instruction. Any value from 0000H to FFFFH can
be set.
RESET input sets CR90 to FFFFH.
Cautions 1. CR90 is designed to be manipulated with a 16-bit memory manipulation instruction.
However, it can also be manipulated with an 8-bit memory manipulation instruction.
When an 8-bit memory manipulation instruction is used to set CR90, it must be
accessed by direct addressing.
2. To overwrite CR90 during a count operation, it is necessary to disable interrupts in
advance, using interrupt mask flag register 1 (MK1). It is also necessary to disable
inversion of the timer output data, using 16-bit timer mode control register 90 (TMC90).
If the value in CR90 is rewritten in the interrupt-enabled state, an interrupt request may
occur at the moment of rewrite.
(2) 16-bit timer counter 90 (TM90)
TM90 is used to count the number of pulses.
The contents of TM90 are read with an 8-bit or 16-bit memory manipulation instruction.
RESET input sets TM90 to 0000H.
Cautions 1. The count becomes undefined when STOP mode is deselected, because the count
operation is performed before oscillation stabilizes.
2. TM90 is designed to be manipulated with a 16-bit memory manipulation instruction.
However, it can also be manipulated with an 8-bit memory manipulation instruction.
When an 8-bit memory instruction is used to manipulate TM90, it must be accessed by
direct addressing.
3. When an 8-bit memory manipulation instruction is used to manipulate TM90, the lower
and higher bytes must be read as a pair, in this order.
(3) 16-bit capture register 90 (TCP90)
TCP90 captures the contents of TM90.
It is set with an 8-bit or 16-bit memory manipulation instruction.
RESET input makes TCP90 undefined.
Caution TCP90 is designed to be manipulated with a 16-bit memory manipulation instruction.
However, it can also be manipulated with an 8-bit memory manipulation instruction. When
an 8-bit memory manipulation instruction is used to manipulate TCP90, it must be
accessed by direct addressing.
(4) 16-bit counter read buffer 90
This buffer is used to latch and hold the count value for TM90.
User’s Manual U15075EJ1V0UM00
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NEC [ NEC ]
