C8051F989-GUR Silicon Labs, C8051F989-GUR Datasheet - Page 287

• Manufacturer Part Number: C8051F989-GUR
• Description: 8-bit Microcontrollers - MCU 4kB 512B RAM
• Manufacturer: Silicon Labs

Specifications of C8051F989-GUR

• Rohs: yes
• Core: 8051
• Data Bus Width: 8 bit
• Processor Series: C8051

25.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is set, Timer 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers oper-
ate in auto-reload mode as shown in Figure 25.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH
holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control for TMR2H. TMR2L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, SmaRTClock divided by 8 or
Comparator 0 output. The Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or
the clock defined by the Timer 2 External Clock Select bits (T2XCLK[1:0] in TMR2CN), as follows:
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows
from 0xFF to 0x00. When Timer 2 interrupts are enabled (IE.5), an interrupt is generated each time
TMR2H overflows. If Timer 2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is gener-
ated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the
TF2H and TF2L flags to determine the source of the Timer 2 interrupt. The TF2H and TF2L interrupt flags
are not cleared by hardware and must be manually cleared by software.
T2MH
0
0
0
0
1
SmaRTClock / 8
Comparator 0
SYSCLK / 12
T2XCLK[1:0]
00
01
10
11
X
T2XCLK[1:0]
00
01
11
Figure 25.5. Timer 2 8-Bit Mode Block Diagram
SYSCLK / 12
SmaRTClock / 8
Reserved
Comparator 0
SYSCLK
SYSCLK
TMR2H Clock
Source
0
1
1
0
M
H
T
3
M
T
3
L
CKCON
M
T
2
H
M
T
2
L
M
T
1
M
T
0
TR2
S
C
A
1
C
S
A
0
Rev. 1.1
TCLK
TCLK
C8051F99x-C8051F98x
TMR2RLH
TMR2RLL
T2ML
TMR2H
TMR2L
0
0
0
0
1
Reload
Reload
T2XCLK[1:0]
00
01
10
11
X
To SMBus
To ADC,
TF2CEN
T2SPLIT
SMBus
TF2LEN
T2XCLK
TF2H
TF2L
TR2
SYSCLK / 12
SmaRTClock / 8
Reserved
Comparator 0
SYSCLK
TMR2L Clock
Source
Interrupt
287