Datasheet

78K0/Ix2 CHAPTER 8 8-BIT TIMER/EVENT COUNTER 51
R01UH0010EJ0500 Rev.5.00 332
Feb 28, 2012
8.5 Cautions for 8-Bit Timer/Event Counter 51
(1) Timer start error
An error of up to one clock may occur in the time required for a match signal to be generated after timer start. This is
because 8-bit timer counter 51 (TM51) are started asynchronously to the count clock.
Figure 8-11. 8-Bit Timer Counter 51 (TM51) Start Timing
Count clock
TM51 count value 00H 01H 02H 03H 04H
Timer start
(2) Reading of 8-bit timer counter 51 (TM51)
TM51 can be read without stopping the actual counter, because the count values captured to the buffer are fixed
when it is read. The buffer, however, may not be updated when it is read immediately before the counter counts up,
because the buffer is updated at the timing the counter counts up.
Figure 8-12. 8-bit Timer Counter 51 (TM51) Read Timing
34H 35H 36H 37H 38H 39H 3AH 3BH
34H 35H 37H 38H 3BH
Count clock
TM51 count value
Read buffer
Read signal