MC68HC705B16CFN Freescale Semiconductor, MC68HC705B16CFN Datasheet - Page 59

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MC68HC705B16CFN

Manufacturer Part Number
MC68HC705B16CFN
Description
IC MCU 2.1MHZ 15K OTP 52-PLCC
Manufacturer
Freescale Semiconductor
Series
HC05r
Datasheet

Specifications of MC68HC705B16CFN

Core Processor
HC05
Core Size
8-Bit
Speed
2.1MHz
Connectivity
SCI
Peripherals
POR, WDT
Number Of I /o
32
Program Memory Size
15KB (15K x 8)
Program Memory Type
OTP
Eeprom Size
256 x 8
Ram Size
352 x 8
Voltage - Supply (vcc/vdd)
4.5 V ~ 5.5 V
Data Converters
A/D 8x8b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
52-PLCC
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

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The programmable timer on the MC68HC05B6 consists of a 16-bit read-only free-running counter,
with a fixed divide-by-four prescaler, plus the input capture/output compare circuitry. The timer can
be used for many purposes including measuring pulse length of two input signals and generating
two output signals. Pulse lengths for both input and output signals can vary from several
microseconds to many seconds. In addition, it works in conjunction with the pulse length
modulation (PLM) system, which can also be referred to as the pulse width modulation system, to
execute two 8-bit D/A PLM (pulse length modulation) conversions, with a choice of two repetition
rates. The timer is also capable of generating periodic interrupts or indicating passage of an
arbitrary multiple of four CPU cycles. A block diagram is shown in
are shown in
The timer has a 16-bit architecture, hence each specific functional segment is represented by two
8-bit registers (except the PLMA and PLMB which use one 8-bit register for each). These registers
contain the high and low byte of that functional segment. Accessing the low byte of a specific timer
function allows full control of that function; however, an access of the high byte inhibits that specific
timer function until the low byte is also accessed.
The 16-bit programmable timer is monitored and controlled by a group of sixteen registers, full
details of which are contained in this section.
Note:
5.1
The key element in the programmable timer is a 16-bit, free-running counter or counter register,
preceded by a prescaler that divides the internal processor clock by four. The prescaler gives the
timer a resolution of 2µs if the internal bus clock is 2 MHz. The counter is incremented during the
low portion of the internal bus clock. Software can read the counter at any time without affecting
its value.
MC68HC05B6
Rev. 4.1
A problem may arise if an interrupt occurs in the time between the high and low bytes
being accessed. To prevent this, the I-bit in the condition code register (CCR) should be
set while manipulating both the high and low byte register of a specific timer function,
ensuring that an interrupt does not occur.
Figure
Counter
5-2,
PROGRAMMABLE TIMER
Figure
5-3,
PROGRAMMABLE TIMER
Figure 5-4
5
and
Figure
5-5.
Figure
5-1, and timing diagrams
Freescale
5-1
5

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