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GR716-DS-UM, May 2019, Version 1.29
20
www.cobham.com/gaisler
GR716
2.2
Digital Architecture Overview
The system is built around three 32-bit AMBA AHB buses; one 32-bit Main AHB bus, one 32-bit
DMA AHB buses and one 32-bit Debug AHB bus. The main bus connects the LEON3FT core with
all other peripheral cores in the design as well as the external memory controllers. Several peripherals
are connected through AMBA AHB/APB bridges where one of the bridges is integrated with the
DMA controller.
The debug AMBA AHB bus connects a UART serial debug communications link to the debug sup-
port unit and also to the rest of the system through an AMBA AHB bridge.
Figure 2.
Simplified architecture and functional block diagram of the microcontroller
2.2.1
Processor core and memory subsystem
The microcontroller implements a LEON3FT 32-bit processor core conforming to the IEEE-1754
(SPARC V8) architecture. The microcontroller is designed for embedded applications, combining
high performance with low complexity and low power consumption. The LEON3FT core has the fol-
lowing main features: 7-stage pipeline with Harvard architecture, hardware multiplier and divider and
on-chip debug support. The LEON3FT processor is enhanced with fault tolerance against SEU errors.
The fault tolerance is focused on the protection of the on-chip RAM, processor register file and pro-
tection of external memory interfaces.
The LEON3FT integer pipeline is implemented with 31 register windows, SEU protection of register
file with zero impact on software timing, and hardware multiply and divide units. The multiplier is a
16x16 hardware multiplier that is iterated four times. Floating-point operations are supported by inte-
gration of a hardware floating-point unit (GRFPU-lite).
Memory protection units are located on the AMBA system bus and on AMBA DMA bus. Each pro-
tection unit monitors access on the AHB bus. When an access is made to a protected area then the pro-
tection unit will assert a signal to the memory controller that will annul the operation and respond to
the AMBA access with an AMBA ERROR response. Four areas can be protected on the system bus
and four areas can be protected on the DMA bus.
Exclusive write permission can be enforced for individual APB peripherals to protect interfaces from
erroneous writes during normal operations.
AHBSTAT
Onchip
ADC &
DAC
Bridge
Bridge
Bridge
Bridge
Bridge
Debug
Unit
(DSU)
I2C
DMA AMBA AHB
AMBA APB 0
Memory
Controller
Serial
Debug
Link
RS232
I2C
SPI
1553 A/B
Mil-1553B
BC/RT/MT
SpaceWire
Links
RMAP
CAN
2.0
LVDS /
LVTTL
CAN N/R
DMA
Controller
I/O Port
LEON3FT
SPARC V8
Mul
Trace
64kB
D-ram
FPU
PacketWire
LVDS /
LVTTL
SPI
GPIO
External
ADC &
DAC
PWM
PWM
UART
RS232
Config &
Status
DMA
Controller
Scrub &
ahbstat
AMBA
128kB
I-ram
REX
Main AMBA AHB
Memory
Prot
Embeeded
Boot ROM
Bridge
IrqCtrl &
Timers
Onchip
ADCDAC
Bridge
SPI2AHB
SPI
I2C2AHB
I2C
SPI4S
SPI
Memory
Controller
Scrubber Bus
PacketWire
Debug Control
Reset /
Clock
Reset /
Watchdog
Clock
DBG AMBA
BO
POR
BO
LDO
NVRAM
Controller
AMBA APB 1
Ext
ADC
SpacWire
TDP
AHBUART
RS232
AMBA APB 2
SPI
Memory
Ext
PROM/SRAM
Memory
NVRAM
AMBA APB 3
Status
and
Control