Motorola MC6805R Series User Manual

Once the EPROM has been programmed and verified, close switch S2 (to remove Vpp and VIHTP)
and close switch S1 (to reset). Disconnect +26 volts and VCC, then remove the EPROM from its
socket.
9.6 EMULATION
The MC68705R3 and MC68705R5 emulate the MC6805R2 and MC6805R3 while the MC68705U3
and MC68705U5 emulate the MC685U2 and MC6805U3 "exactly." MC6805R2, MC6805U2,
MC6805R3,
and MC6805U3 mask features are implemented in the mask option register (MOR)
EPROM byte. There are a few minor exceptions to the exactness of emulation which are listed
below.
1. The MC6805R21 MC6805U2 and MC6805R31 MC6805U3 "future ROM" areas are imple-
mented in the MC68705R3/MC68705U3 and MC68705R5/MC68705U5 and these 1728 bytes
must
be left unprogrammed to accurately simulate the MC6805R2/MC6805U2 and
MC6805R3/MC6805U3. (The MC6805R2/MC6805U2 and MC6805R3/MC6805U3 read all
zeros from this area.)
2. The reserved ROM areas have different data stored in them and this data is subject to
change
without notice. The MC6805R2, MC6805U2, MC6805R3, and MC6805U3 use the
reserved
ROM for the self-check feature while the MC68705R3, MC68705U3, MC68705R5,
and MC68705U5 use this area for the bootstrap program.
3. The MC6805R2/MC6805U2 and MC6805R3/MC6805U3 read all ones in their 48 byte "future
RAM" area. This RAM is not implemented in the MC6805R2/MC6805U2 and
MC6805R3/MC6805U3 mask ROM version, but is implemented in the EPROM version
(M C68705R31 M C68705U3 and M C68705R51 M C68705U5) .
4. The Vpp line (pin 7) in the MC68705R3/MC68705U3 and MC68705R5/MC68705U5 EPROM
versions is tied to VCC for normal operation. In the MC6805R2/MC6805U2 and
MC6805R3/MC6805U3 mask ROM versions, pin 7 is grounded in normal operation.
5. The LVI feature is not available in the EPROM version.
6. The MC68705R3/MC68705U3 and MC68705R5/MC68705U5 EPROM versions do not func-
tion
in the MEX6805 Support System. In normal operation, all pin functions are the same as
on the MC6805R2/MC6805U2 and MC6805R3/MC6805U3 mask ROM versions, except for
pin 7
as previously noted.
The operation
of all other circuitry has been exactly duplicated or designed to function exactly the
same way
in all devices including interrupts, timer, data ports, and data direction registers (DDRs).
9-6

Motorola MC6805R Series Specifications

General

Brand	Motorola
Model	MC6805R Series
Category	Computer Hardware
Language	English