HCS12COREUG View Datasheet(PDF) - Motorola => Freescale
Part Name
Description
MFG CO.
'HCS12COREUG' PDF : 124 Pages View PDF
MC9S12H256 Device User Guide — V01.14
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 high the EXTAL pin is configured for an
external clock drive. If input is a logic low an oscillator circuit is configured on EXTAL and XTAL. Since
this pin is an input with a pull-down device during reset, if the pin is left floating, the default configuration
is an oscillator circuit on EXTAL and XTAL.
During MCU expanded modes of operation, the NOACC signal, when enabled, is used to indicate that the
current bus cycle is an unused or “free” cycle. This signal will assert when the CPU is not using the bus.
2.3.11 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.
2.3.12 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.
2.3.13 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.
2.3.14 PE3 / FP21 / LSTRB / TAGLO — Port E I/O Pin 3
PE3 is a general purpose input or output pin. It can be configured as frontplane segment driver output FP21
of the LCD module. In MCU expanded modes of operation, LSTRB is 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.
2.3.15 PE2 / FP20 / R/W — Port E I/O Pin 2
PE2 is a general purpose input or output pin. It can be configured as frontplane segment driver output FP20
of the LCD module. In MCU expanded modes of operations, this pin performs the read/write output signal
for the external bus. It indicates the direction of data on the external bus.
2.3.16 PE1 / IRQ — Port E Input Pin 1
PE1 is a general purpose input pin and also 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.
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