DSPIC30F3011-30I/PT Microchip Technology Inc., DSPIC30F3011-30I/PT Datasheet - Page 47

• Manufacturer Part Number: DSPIC30F3011-30I/PT
• Description: 16 BIT MCU/DSP 44LD 30MIPS 24 KB FLASH
• Manufacturer: Microchip Technology Inc.
• Type: DSPr

Specifications of DSPIC30F3011-30I/PT

• A/d Inputs: 9-Channels, 10-Bit
• Cpu Speed: 30 MIPS
• Eeprom Memory: 1K Bytes
• Input Output: 30
• Interface: I2C/SPI/UART, USART
• Ios: 30
• Memory Type: Flash
• Number Of Bits: 16
• Package Type: 44-pin TQFP
• Programmable Memory: 24K Bytes
• Ram Size: 1K Bytes
• Timers: 5-16-bit, 2-32-bit
• Voltage, Range: 2.5-5.5
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

4.3
4.3.1
In order to maximize data space, EA calculation and
operand fetch time, the X data space read and write
accesses are partially pipelined. The latter half of the
read phase overlaps the first half of the write phase of
an instruction, as shown in Section 2.
Address register data dependencies, also known as
‘Read After Write’ (RAW) dependencies, may therefore
arise between successive read and write operations
using common registers. They occur across instruction
boundaries and are detected by the hardware.
An example of a RAW dependency is a write operation
(in the current instruction) that modifies W5, followed
by a read operation (in the next instruction) that uses
W5 as a source address pointer. W5 will not be valid for
the read operation until the earlier write completes.
This problem is resolved by stalling the instruction exe-
cution for one instruction cycle, thereby allowing the
write to complete before the next read is started.
TABLE 4-2:
 2004 Microchip Technology Inc.
Direct
Direct
Direct
Indirect
Indirect
Indirect
Indirect
Indirect
Indirect with Pre- or
Post-Modification
Indirect with Pre- or
Post-Modification
Indirect with Pre- or
Post-Modification
Addressing Mode
Destination
Using Wn
Instruction Stalls
INTRODUCTION
RAW DEPENDENCY RULES (DETECTION BY HARDWARE)
Direct
Indirect
Indirect with Pre- or
Post-Modification
Direct
Indirect
Indirect
Indirect with Pre- or
Post-Modification
Indirect with Pre- or
Post-Modification
Direct
Indirect
Indirect with Pre- or
Post-Modification
Source Addressing
Mode Using Wn
No Stall ADD.w
No Stall ADD.w
No Stall ADD.w
No Stall ADD.w
No Stall ADD.w
Status
Stall
Stall
Stall
Stall
Stall
Stall
Preliminary
MOV.w
ADD.w
MOV.w
ADD.w
MOV.w
MOV.w
MOV.w
ADD.w
MOV.w
MOV.w
ADD.w
MOV.w
MOV.w
ADD.w
MOV.w
ADD.w
MOV.w
4.3.2
During the instruction pre-decode, the core determines
if any address register dependency is imminent across
an instruction boundary. The stall detection logic com-
pares the W register (if any) used for the destination EA
of the instruction currently being executed, with the W
register to be used by the source EA (if any) of the pre-
fetched instruction. As the W registers are also memory
mapped, the stall detection logic also derives an SFR
address from the W register being used by the destina-
tion EA, and determines whether this address is being
issued during the write phase of the instruction cur-
rently being executed.
When it observes a match between the destination and
source registers, a set of rules are applied to decide
whether or not to stall the instruction by one cycle.
Table 4-2 lists out the various RAW conditions which
cause an instruction execution stall.
[W2++], W3
[W2], W3
W0, W1, [W2] ; W2=0x0004 (mapped W2)
W0, W1, [W2] ; W2=0x0004 (mapped W2)
W0, W1, W2
W2, W3
W0, W1, W2
[W2], W3
W0, W1, W2
[W2++], W3
W0, W1, [W2]
W2, W3
W0, W1, [W2]
[W2], W3
W0, W1, [W2]
[W2++], W3
W0, W1, [W2++]
W2, W3
W0, W1, [W2++]
[W2], W3
W0, W1, [W2++]
[W2++], W3
RAW DEPENDENCY DETECTION
; (i.e., if W2 = addr. of W2)
; (i.e., if W2 = addr. of W2)
(Wn = W2)
Examples
dsPIC30F
DS70082G-page 45