Updating Application from RCM5700 to RCM6700 Datasheet by Digi

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Updating Your Application from the
RCM5700 to the RCM6700
Rabbit® MiniCore™ Family
This technical note describes some of the common considerations and concerns that may be encountered in
updating a Rabbit application from the RCM5700/RCM5710/RCM5750/RCM5760 (collectively,
RCM57xx) MiniCore family to the RCM6700/RCM6710/RCM6750/RCM6760 (collectively, RCM67xx)
MiniCore family.
Comparing the RCM57xx and the RCM67xx Rabbit MiniCores
Dynamic C® Versions
RCM57xx and RCM67xx MiniCores are supported by the following Dynamic C versions:
* Although support for RCM6750/RCM6760 boards is first mentioned in the Dynamic C 10.64 release
notes, a pre-production change to RCM6750/RCM6760 hardware requires corresponding software
changes that are supported by Dynamic C 10.66 and later versions.
Binary Incompatibility
RCM57xx applications are not binary compatible with the corresponding RCM67xx board. This binary
incompatibility is due to a number of factors, with the primary reason being the difference between the
program storage flash devices. Where the RCM57xx stores and runs its application in its parallel program
flash, the RCM67xx stores its application in serial program flash buts runs the application in its internal
fast RAM.
MiniCore Model Supported by Dynamic C Version
RCM5700/RCM5710 10.44 and later
RCM5750/RCM5760 10.56 and later
RCM6700/RCM6710 10.64 and later
RCM6750/RCM6760 10.66 and later*
Bottom .3 3 v Rx+ Rx— Pin 8 ACTI +2.5v PE1 PE3 Pas IRESEYJN PD1 PDJ PC1 PCS PCS/RXB [RESET PBS P55 P57 PA1 PAS PAS PA7 VBAT_EXT P5116 LKA Pcs/rxA PC7IR xA +3.3 V 52 Top 6ND Txo Tx— LNK PEU P52 P55 PE7 PDu PD2 P00 P02 PC4/TXE PBD/SCLK PEZ P54 PEG PAu PAZ PA4 PAS IIORD IIOWR sYATUs SMODE 6ND Pin 7 Pin 27 51
Main Oscillator Maximum and Minimum Clock Rates
Another significant reason for binary incompatibility is the difference between Rabbit 5000 and Rabbit
6000 CPU clocks. With regard to maximums, an RCM57xx board is limited to its 25 MHz main oscillator
clock being doubled to 50 MHz. In contrast, an RCM67xx board's PLL is by default set to multiply the 25
MHz main oscillator rate to provide a 187.5 MHz CPU clock frequency.
On the minimums side, RCM57xx applications may operate in one of the Rabbit 5000 CPU's low-power
"sleepy" modes, potentially using as low as a 2.048 KHz CPU clock frequency. However, an RCM67xx's
Rabbit 6000 CPU can only operate from its internal 1MByte fast RAM at a minimum clock frequency of
about 12 MHz; below this CPU clock rate the internal fast RAM content (including application code) is
not refreshed often enough to be retained.
Edge Connector Changes
Pinout Diagram
Edge Connector Pin 7
Edge connector pin 7 on an RCM57xx board carries only an Ethernet link output signal.The RCM6700/
RCM6750 boards' edge connector pin 7 carries a combined Ethernet link plus activity output signal by
default, via the Rabbit CPU's PG0. On RCM6700/RCM6750 boards, PG0 may be used instead for GPIO
on edge connector pin 7 only when the DISABLE_ENET_STATUS macro is defined in Dynamic C's Proj-
ect Options' Defines box. On RCM6710/RCM6760 boards, PG0 is always available for GPIO on edge
connector pin 7.
Edge Connector Pin 8
On an RCM57xx board, edge connector pin 8 carries an Ethernet activity output signal. RCM67xx boards'
edge connector pin 8 carries a 2.5VDC Ethernet supply voltage.
Edge Connector Pin 27
Edge connector pin 27 on an RCM57xx is direct connected (via a 0-Ohm jumper) to Rabbit's PB0/SCLKB
pin and is generally available for GPIO, with the following caveat:
On RCM5750/RCM5760 boards only, a 49.9 Ohm isolation resistor is placed between the serial
flash's SCK input and the other on-MiniCore PB0/SCLKB connections. An RCM5750/RCM5760
application which uses PB0/SCLKB for both off-MiniCore connections and on-MiniCore serial flash
communication is responsible for implementing a suitable mutex to protect the shared PB0/SCLKB
Connector Board Default Use GPIO Use
Pin 7
RCM57xx Ethernet link No
RCM6750 Combined Ethernet link plus
activity output signal
PG0 when
defined. See “Edge Connector Pin
7” below.
RCM6760 None PG0
Pin 8 RCM57xx Ethernet activity output signal No
RCM67xx 2.5VDC Ethernet supply voltage No
Pin 27
RCM5710 None PB0/SCLKB
Synchronous serial clock
connected to the on-MiniCore
data storage serial flash
PB0/SCLKB is a shared resource.
See “Edge Connector Pin 27”
RCM67xx Synchronous serial clock
connected to the on-MiniCore
serial boot flash
PB0/SCLKB is a shared resource.
During boot-up the Rabbit CPU
requires exclusive, unimpeded
access to SCLKB. See “Edge
Connector Pin 27” below.
An RCM67xx's edge connector pin 27 is isolated by a 49.9 Ohm resistor from the other on-MiniCore
PB0_SCLKB connections. In particular, an RCM67xx's serial boot capability relies on the direct connec-
tion between the serial flash's SCK and the Rabbit CPU's PB0_SCLKB together with their isolation from
edge connector pin 27. Because the PB0_SCLKB output is extremely active during the RCM67xx's boot-
up from serial flash, if edge connector pin 27 is externally connected at all, it is strongly recommended that
its use be restricted to that of a serial clock for additional external SPI devices. Note that if PB0_SCLKB is
shared between the on-MiniCore serial boot flash and any other external use, that the RCM67xx applica-
tion is responsible for implementing a suitable mutex to protect the shared PB0_SCLKB resource.
SPI Port Sharing Mutual Exclusion (Mutex) Examples
Introduced in Dynamic C 10.66, the Samples\RCM6700\Shared_SPI folder contains example programs
that demonstrate use of an extensible mutex to allow sharing of the SPI serial port (B) between several dif-
ferent devices. Standard samples are provided for both cooperative and preemptive multitasking.
Rabbit — A Digi International Brand

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