Mitsubishi Motors DS5000TK - Manual (Page 143)

USER’S GUIDE
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PARALLEL PROGRAMMING CONCERNS
Dallas Semiconductor highly recommends using the
serial load mode for programming the DS5000. It has
proven highly reliable and easy to use. In the event that
parallel programming is still desirable to some users,
several incompatibilities have been discovered in con-
ventional device programmers. The following is a sum-
mary of these incompatibilities:
1. The DS5000 is a fully CMOS device, and was actu-
ally designed to be pin–compatible with the
80C51/87C51 as opposed to the 8051/8751. As a re-
sult there is a subtle difference between these two
devices. This has to do with the oscillator input pins,
XTAL1 and XTAL2. On the CMOS devices, XTAL1
is the pin which is driven in the external drive config-
uration. On NMOS devices, XTAL2 is driven for the
external clock configuration. This difference has no
effect when a crystal is tied to the pins for an external
time base. However, many programming systems
use the external drive configuration in order to main-
tain the ability to program multiple types of devices
in a single 40–pin socket. For this reason, the
DS5000 will not operate correctly in a 8751–compat-
ible socket which uses the external clock mode.
2. The 87C51 data sheet specifies a “fast” program-
ming timing algorithm for programming the locations
in its on–chip EPROM memory. This algorithm is
identical to the 8751 Program mode specification
except for the number and duration of ALE low
pulses during a “Program Byte” state. There are 25
pulses specified, each with a low time of 90 to 110
µ
s following by a minimum high time of 10
µ
s. Since
the Parallel Load mode is partially implemented us-
ing internal ROM firmware, the 87C51 fast program-
ming algorithm is incompatible with the DS5000.
Programming systems which implement this algo-
rithm will not correctly program a DS5000.
3. Also since the Parallel Program mode is partially
firmware based, a minimum recovery time is re-
quired between back–to–back Program Byte
strobes and between a Program Byte strobe fol-
lowed by a Verify strobe.
4. Many programming systems apply V
CC
voltage dur-
ing programming and remove it when programming
is completed. This operation is compatible with the
DS5000 if the Power–On Reset time spec (t
POR
) is
met before programming begins. Since there is no
similar specification on the 8751 or on the 87C51,
some programming systems may not meet the
DS5000’s requirements and Program strobe pulses
may not be recognized by the DS5000.
5. The DS5000 is compatible with either the 21V V
PP
of the 8751 or the 12V V
PP
of the 87C51. However,
some programming systems sample the current that
is drawn during programming on the V
CC
pin and/or
on the V
PP
pin. An 8751 is specified to draw a maxi-
mum of 30 mA of I
PP
current during programming,
while an 87C51 is specified for a maximum of 50 mA.
A DS5000 will draw a maximum of only 15 mA of I
PP
current during programming. As a result, these pro-
gramming systems may erroneously report that the
device is incorrectly installed in the socket.
Because of the limitations cited above, Dallas Semicon-
ductor recommends that the Serial Bootstrap Loader be
used for initial program loading of the DS5000.
RPC PROGRAM MODE OPERATION
The DS5001FP and DS5002FP series offer high–speed
programming mode with many of the benefits of the
Serial Loader. Like the Serial mode, it is primarily
intended as an in–system technique but can be used in
a fixture. This mode uses the RPC (8042) slave inter-
face to perform a high speed parallel load. When the
PROG pin is pulled to a logic 0, the Bootstrap ROM will
begin looking for an ASCII carriage return. This can
come in via the serial port or the RPC port. The RPC
port is accessed as shown in the section on Parallel I/O.
If the RPC buffer is written with a 0Dh, this will cause the
loader to respond with its banner and prompt using this
same interface. An external microprocessor is
assumed to have written and read these values. The
RPC loader implements the same command interface
and syntax as the Serial Loader. The only difference is
the speed at which data can be written, and the lack of a
baud rate consideration. As bytes are written into the
buffer, they will be acted upon. Handshaking will be
used as described in the Parallel I/O section.
The RPC mode requires no super–voltage pulses. The
CS, RD, and WR strobes control the transfer of data
between the DS5001 and the host. This protocol makes
the DS5001 ideal for PC based applications, but any
host processor can perform the loading.