Registers
MC68HC812A4 Data Sheet, Rev. 7
Freescale Semiconductor
69
6.3.11 Port E Assignment Register
Read: Anytime, if register is in the map
Write: Varies from bit to bit if register is in the map
The PEAR register selects between the general-purpose I/O functions and the alternate bus-control
functions of port E. The alternate bus-control functions override the associated DDRE bits.
The reset condition of this register depends on the mode of operation.
In normal single-chip mode, port E is general-purpose I/O.
In special single-chip mode, the E-clock is enabled as a timing reference, and the rest of port E is
general-purpose I/O.
In normal expanded modes, the E-clock is configured for its alternate bus-control function, and the
other bits of port E are general-purpose I/O. The reset vector is located in external memory and the
E-clock may be required for this access. If R/W is needed for external writable resources, PEAR
can be written during normal expanded modes.
In special expanded modes, IPIPE1, IPIPE0, E, R/W, and LSTRB are configured as bus-control
signals.
In peripheral mode, the PEAR register is not accessible for reads or writes. However, the PLLTE control
bit is cleared to configure PE6 as a test output from the PLL module.
ARSIE — Auxiliary Reset Input Enable Bit
Write anytime.
1 = PE7 is a high-true reset input; reset timing is the same as that of the low-true RESET pin.
0 = PE7 is general-purpose I/O.
PLLTE — PLL Testing Enable Bit
Normal modes: Write never
Special modes: Write anytime except the first time
1 = PE6 is a test signal output from the PLL module (no effect in single-chip or normal expanded
modes); PIPOE = 1 overrides this function and forces PE6 to be a pipe status output signal.
0 = PE6 is general-purpose I/O or pipe output.
Address: $000A
Bit 7
6
5
4321
Bit 0
Read:
ARSIE
PLLTE
PIPOE
NECLK
LSTRE
RDWE
0
Write:
Reset:
Special single-chip:
001
01100
Special expanded narrow:
001
01100
Peripheral:
010
10000
Special expanded wide:
001
01100
Normal single-chip
000
10000
Normal expanded narrow:
000
00000
Normal expanded wide:
000
00000
Figure 6-11. Port E Assignment Register (PEAR)