EZ80F91NA050EC Zilog, EZ80F91NA050EC Datasheet - Page 131

• Manufacturer Part Number: EZ80F91NA050EC
• Description: IC ACCLAIM MCU 256KB 144-BGA
• Manufacturer: Zilog
• Series: eZ80® Acclaim!®r

Specifications of EZ80F91NA050EC

• Core Processor: Z8
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: Ethernet, I²C, IrDA, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 256KB (256K x 8)
• Program Memory Type: FLASH
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 144-LBGA
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 50 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 16 bit
• Operating Supply Voltage: 3 V to 3.6 V
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• For Use With: 269-4712 - KIT DEV ENCORE 32 SERIES269-4671 - BOARD ZDOTS SBC Z80ACCLAIM PLUS269-4561 - KIT DEV FOR EZ80F91 W/C-COMPILER269-4560 - KIT DEV FOR EZ80F91 W/C-COMPILER
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -
• Lead Free Status / Rohs Status: No
• Other names: 269-3250

PS019215-0910
Basic Timer Operation
Basic timer operation is controlled by a timer control register and a programmable reload
value. The CPU uses the control register to setup the prescaling, the input clock source,
the end-of-count behavior, and to start the timer. The 16-bit reload value is used to 
determine the duration of the timer’s count before either halting or reloading.
After choosing a timer period and writing the appropriate values to the reload registers, the
CPU must set the timer enable bit (TMRx_CTL[TIM_EN]) by allowing the count to
begin. The reload bit (TMRx_CTL[RLD]) must also be asserted so that the timer counts
down from the reload value rather than from
assertion of the reload bit, the timer loads with the 16-bit reload value and begins counting
down. The reload bit is automatically cleared after the loading operation. The timer is
enabled and reloaded on the same cycle; however, the timer does not require disabling to
reload and reloading is performed at any time. It is also possible to halt the timer by deas-
serting the timer enable bit and resuming the count at a later time from the same point by
reasserting the bit.
Reading the Current Count Value
The CPU reads the current count value when the timer is running. Because the count is a
16-bit value, the hardware latches the value of the upper byte into temporary storage when
the lower byte is read. This value in temporary storage is the value returned when the
upper byte is read. Therefore, the software must read the lower byte first. If it attempts to
read the upper byte first, it does not obtain the current upper byte of the count. Instead, it
obtains the last latched value. This Read operation does not affect timer operation.
Setting Timer Duration
There are three factors to consider while determining Programmable Reload Timer 
duration: clock frequency, clock divider ratio, and initial count value. Minimum duration
of the timer is achieved by loading
0000h
0000h
bits of the control register, the clock is either the system clock, or an on-chip RC oscillator
output or an input from a pin.
The time-out period of the timer is returned by the following equation:
To calculate the time-out period with the above equation while using an initial value of
0000h
Time-Out Period =
, because the timer first rolls over to
, enter a reload value of 65536 (
before the end-of-count is signaled. Depending on the TMRx_CTL[CLK_SEL]
Clock Divider Ratio x Reload Value
System Clock Frequency
0001h
FFFFh
. Maximum duration is achieved by loading
FFFFh
0000h
+ 1).
and then continues counting down to
. On the system clock cycle, after the
Programmable Reload Timers
Product Specification
eZ80F91 MCU
122