MC9S12A128 Datasheet, PDF (30/92 Pages) Motorola, Inc – Microcontroller unit (MCU)

MC9S12A128 Device Guide — V01.01
The XCLKS input selects between an external clock or oscillator configuration. The state of this pin is
latched at the rising edge of RESET. If the input is a logic low the EXTAL pin is configured for an external
clock drive. If input is a logic high an oscillator circuit is configured on EXTAL and XTAL. Since this pin
is an input with a pull-up device, if the pin is left floating, the default configuration is an oscillator circuit
on EXTAL and XTAL.
2.3.14 PE6 / MODB / IPIPE1 — Port E I/O Pin 6
PE6 is a general purpose input or output pin. It is used as a MCU operating mode select pin during reset.
The state of this pin is latched to the MODB bit at the rising edge of RESET. This pin is shared with the
instruction queue tracking signal IPIPE1. This pin is an input with a pull-down device which is only active
when RESET is low.
2.3.15 PE5 / MODA / IPIPE0 — Port E I/O Pin 5
PE5 is a general purpose input or output pin. It is used as a MCU operating mode select pin during reset.
The state of this pin is latched to the MODA bit at the rising edge of RESET. This pin is shared with the
instruction queue tracking signal IPIPE0. This pin is an input with a pull-down device which is only active
when RESET is low.
2.3.16 PE4 / ECLK — Port E I/O Pin 4
PE4 is a general purpose input or output pin. It can be configured to drive the internal bus clock ECLK.
ECLK can be used as a timing reference.
2.3.17 PE3 / LSTRB / TAGLO — Port E I/O Pin 3
PE3 is a general purpose input or output pin. In MCU expanded modes of operation, LSTRB can be used
for the low-byte strobe function to indicate the type of bus access and when instruction tagging is on,
TAGLO is used to tag the low half of the instruction word being read into the instruction queue.
2.3.18 PE2 / R/W — Port E I/O Pin 2
PE2 is a general purpose input or output pin. In MCU expanded modes of operations, this pin drives the
read/write output signal for the external bus. It indicates the direction of data on the external bus.
2.3.19 PE1 / IRQ — Port E Input Pin 1
PE1 is a general purpose input pin and the maskable interrupt request input that provides a means of
applying asynchronous interrupt requests. This will wake up the MCU from STOP or WAIT mode.
2.3.20 PE0 / XIRQ — Port E Input Pin 0
PE0 is a general purpose input pin and the non-maskable interrupt request input that provides a means of
applying asynchronous interrupt requests. This will wake up the MCU from STOP or WAIT mode.
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