HD404639R Datasheet, PDF (67/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

HD404639R Series
• Timer write register B (TWBL: $00A, TWBU: $00B): Write-only register consisting of the lower digit
(TWBL) and the upper digit (TWBU) as shown in figures 46 and 47. The lower digit is reset to $0 by
MCU reset, but the upper digit value is invalid.
Timer B is initialized by writing to timer write register B. In this case, the lower digit (TWBL) must be
written to first, but writing only to the lower digit does not change the timer B value. Timer B is
initialized to the value in timer write register B at the same time the upper digit (TWBU) is written to.
When timer write register B is written to again and if the lower digit value needs no change, writing
only to the upper digit initializes timer B.
Timer write register B (lower digit) (TWBL: $00A)
Bit
Initial value
Read/Write
Bit name
3
0
W
TWBL3
2
0
W
TWBL2
1
0
W
TWBL1
0
0
W
TWBL0
Figure 46 Timer Write Register B Lower Digit (TWBL)
Timer write register B (upper digit) (TWBU: $00B)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
W
W
W
W
TWBU3 TWBU2 TWBU1 TWBU0
Figure 47 Timer Write Register B Upper Digit (TWBU)
• Timer read register B (TRBL: $00A, TRBU: $00B): Read-only register consisting of the lower digit
(TRBL) and the upper digit (TRBU) that holds the count of the timer B upper digit (figures 48 and 49).
The upper digit (TRBU) must be read first. At this time, the count of the timer B upper digit is
obtained, and the count of the timer B lower digit is latched to the lower digit (TRBL). After this, by
reading TRBL, the count of timer B when TRBU is read can be obtained.
Timer read register B (lower digit) (TRBL: $00A)
Bit
Initial value
Read/Write
Bit name
3
2
1
0
Undefined Undefined Undefined Undefined
R
R
R
R
TRBL3 TRBL2 TRBL1 TRBL0
Figure 48 Timer Read Register B Lower Digit (TRBL)
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