pic32mx320f032h Microchip Technology Inc., pic32mx320f032h Datasheet - Page 22

• Manufacturer Part Number: pic32mx320f032h
• Description: 64/100-pin General Purpose And Usb 32-bit Flash Microcontrollers
• Manufacturer: Microchip Technology Inc.

PIC32MX3XX/4XX
3.2
The PIC32MX3XX/4XX Family core contains several
logic blocks working together in parallel, providing an
efficient high performance computing engine. The fol-
lowing blocks are included with the core:
• Execution Unit
• Multiply/Divide Unit (MDU)
• System Control Coprocessor (CP0)
• Fixed Mapping Translation (FMT)
• Dual Internal Bus interfaces
• Power Management
• MIPS16e Support
• Enhanced JTAG (EJTAG) Controller
3.2.1
The PIC32MX3XX/4XX Family core execution unit
implements a load/store architecture with single-cycle
ALU operations (logical, shift, add, subtract) and an
autonomous multiply/divide unit. The core contains
thirty-two 32-bit general purpose registers used for
integer operations and address calculation. One addi-
tional register file shadow set (containing thirty-two reg-
isters) is added to minimize context switching overhead
during interrupt/exception processing. The register file
consists of two read ports and one write port and is fully
bypassed to minimize operation latency in the pipeline.
• 32-bit adder used for calculating the data address
• Address unit for calculating the next instruction
• Logic for branch determination and branch target
• Load aligner
• Bypass multiplexers used to avoid stalls when
• Leading Zero/One detect unit for implementing the
• Arithmetic Logic Unit (ALU) for performing bitwise
• Shifter and Store Aligner
DS61143F-page 20
The execution unit includes:
address
address calculation
executing
producing instructions are followed closely by
consumers of their results
CLZ and CLO instructions
logical operations
Architecture Overview
EXECUTION UNIT
instructions
streams
where
data
Preliminary
3.2.2
The PIC32MX3XX/4XX Family core includes a multi-
ply/divide unit (MDU) that contains a separate pipeline
for multiply and divide operations. This pipeline oper-
ates in parallel with the integer unit (IU) pipeline and
does not stall when the IU pipeline stalls. This allows
MDU operations to be partially masked by system stalls
and/or other integer unit instructions.
The high-performance MDU consists of a 32x16 booth
recoded multiplier, result/accumulation registers (HI
and LO), a divide state machine, and the necessary
multiplexers and control logic. The first number shown
(‘32’ of 32x16) represents the rs operand. The second
number (‘16’ of 32x16) represents the rt operand. The
PIC32MX core only checks the value of the latter (rt)
operand to determine how many times the operation
must pass through the multiplier. The 16x16 and 32x16
operations pass through the multiplier once. A 32x32
operation passes through the multiplier twice.
The MDU supports execution of one 16x16 or 32x16
multiply operation every clock cycle; 32x32 multiply
operations can be issued every other clock cycle.
Appropriate interlocks are implemented to stall the
issuance of back-to-back 32x32 multiply operations.
The multiply operand size is automatically determined
by logic built into the MDU.
Divide operations are implemented with a simple 1 bit
per clock iterative algorithm. An early-in detection
checks the sign extension of the dividend (rs) operand.
If rs is 8 bits wide, 23 iterations are skipped. For a 16-
bit-wide rs, 15 iterations are skipped, and for a 24-bit-
wide rs, 7 iterations are skipped. Any attempt to issue
a subsequent MDU instruction while a divide is still
active causes an IU pipeline stall until the divide oper-
ation is completed.
Table 3-1 lists the repeat rate (peak issue rate of cycles
until the operation can be reissued) and latency (num-
ber of cycles until a result is available) for the PIC32MX
core multiply and divide instructions. The approximate
latency and repeat rates are listed in terms of pipeline
clocks.
MULTIPLY/DIVIDE UNIT (MDU)
© 2009 Microchip Technology Inc.