14 8-BIT TIMERS (T8)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
14-1
8-bit Timers (T8)
14
T8 Module Overview
14.1
The S1C33L26 incorporates an eight-channel 8-bit timer module (T8).
The features of T8 are listed below.
• 8-bit presettable down counter with an 8-bit reload data register for setting the preset value
• The count clock is selectable from 15 clocks output from the prescaler.
• Generates the USI/USIL operating clocks (transfer clock source) and A/D trigger signal from the counter under-
flow signals.
• Generates an underflow interrupt signal to the interrupt controller (ITC).
• Any desired time intervals and serial transfer rates can be programmed by selecting an appropriate count clock
and preset value.
• Ch.0 to Ch.3 support fine mode to minimize transfer rate errors.
Figure 14.1.1 shows the T8 configuration.
Reload data register
T8_TR
x
PRUN
DF[3:0]
PCLK/1–PCLK/16K
Underflow
Run/stop control
Internal data bus
Fine mode setting (Ch.0 to Ch.3)
Interrupt request
A/D trigger signal
To ITC
To USI (from T8 Ch.0)
To USIL (from T8 Ch.3)
To ADC10 (from T8 Ch.2)
From PSC Ch.0 to T8 Ch.0/2/4/6
From PSC Ch.1 to T8 Ch.1/3/5/7
Timer reset
Serial transfer clock
Down counter
T8_TC
x
Control circuit
PRESER
TFMD[3:0]
8-bit Timer Ch.
x
Count clock select
1.1 T8 Configuration (one channel)
Figure 14.
T8 consists of an 8-bit presettable down counter and an 8-bit reload data register holding the preset value. The
timer counts down from the initial value set in the reload data register and outputs an underflow signal when the
counter underflows. The underflow signals are used to generate an interrupt, USI clocks, and an A/D trigger signal.
The underflow cycle can be programmed by selecting the prescaler clock and reload data, enabling the application
program to obtain time intervals and serial transfer speeds as required. Ch.0 to Ch.3 support fine mode to minimize
transfer rate errors.
Note: Eight channels of T8 module have the same functions except for the control register addresses
and fine mode control bit. The description in this chapter applies to all channels otherwise unless
specified. The ‘
x
’ in the register name refers to the channel number (0 to 7).
Example: T8_CTL
x
register
Ch.0: T8_CTL0 register
Ch.1: T8_CTL1 register
Ch.2: T8_CTL2 register
:
Ch.7: T8_CTL7 register