MC68HC11PH8 Datasheet, PDF (136/264 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

The real-time interrupt (RTI) is a programmable periodic interrupt circuit that permits pacing of the
execution of software routines by selecting one of four interrupt rates. It may be clocked by the
16-bit timer (ST4XCK/2¹⁵) or by the underflow of 8-bit modulus timer A (CLK64), depending on
whether or not the PLL system is active (see Figure 8-1, Figure 8-2 and Section 8.1.5).
The COP watchdog clock input may be tapped off from the free-running counter chain
(ST4XCK/2¹⁷), or may be the underflow of the 8-bit modulus timer A (CLK64/4), depending on
whether or not the PLL system is active (see Figure 8-1, Figure 8-2 and Section 8.1.6). The COP
automatically times out unless it is serviced within a specific time by a program reset sequence. If
the COP is allowed to time out, a reset is generated, which drives the RESET pin low to reset the
MCU and the external system (see Section 10).
The LCD module can drive up to four LCD segments, and may be clocked by the 16-bit timer
(ST4XCK/2¹⁸), or by the underflow of the 8-bit modulus timer A (CLK64 or CLK64/8), depending on
whether or not the PLL system is active (see Figure 8-1, Figure 8-2 and Section 2).
Table 8-1 Timer resolution and capacity
Clock
4.0MHz 8.0MHz 12.0MHz 16.0MHz
ST4XCK
Crystal⁽¹⁾
Control bits 1.0MHz 2.0MHz 3.0MHz 4.0MHz ST4XCK/4
Clock
PR[1:0] 1000ns 500ns 333ns 250ns 4/ST4XCK
Period
8
00
1.0µs 500ns 333ns 250ns 4/ST4XCK Ð resolution
65.536ms 32.768ms 21.845ms 16.384ms 2¹⁸/ST4XCK Ð overßow
01
4.0µs 2.0µs 1.333µs 1.0µs 16/ST4XCK Ð resolution
262.14ms 131.07ms 87.381ms 65.536ms 2²⁰/ST4XCK Ð overßow
10
8.0µs 4.0µs 2.667µs 2.0µs 32/ST4XCK Ð resolution
524.29ms 262.14ms 174.76ms 131.07ms 2²¹/ST4XCK Ð overßow
11
16.0µs 8.0µs 5.333µs 4.0µs 64/ST4XCK Ð resolution
1049 ms 524.29ms 349.53ms 262.14ms 2²²/ST4XCK Ð overßow
(1) Crystal frequencies are valid only if the PLL is not active.
MOTOROLA
8-2
TIMING SYSTEM
TPG
MC68HC11PH8