MOD5234-100IR NetBurner Inc, MOD5234-100IR Datasheet - Page 115

• Manufacturer Part Number: MOD5234-100IR
• Description: MOD5234 10/100 ETHERNET MODULE
• Manufacturer: NetBurner Inc
• Type: Controllers & Processorsr

Specifications of MOD5234-100IR

• Interface: I²C, SPI, UART
• Voltage - Supply: 2.5V
• Mounting Type: Surface Mount
• Package / Case: Module
• Product: Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Format: -
• Baud Rates: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: Q4483564

4.4.1.1
This section describes behavior when the fractional mode is used (MACSR[F/I] is set).
4.4.1.1.1
When the processor is in fractional mode, there are two operations during which rounding can
occur.
To understand the round-to-nearest-even method, consider the following example involving the
rounding of a 32-bit number, R0, to a 16-bit number. Using this method, the 32-bit number is
rounded to the closest 16-bit number possible. Let the high-order 16 bits of R0 be named R0.U and
the low-order 16 bits be R0.L.
Freescale Semiconductor
• Execution of a store accumulator instruction (MOV.L ACCx,Rx). The lsbs of the 48-bit
• Execution of a MAC (or MSAC) instruction with 32-bit operands. If MACSR[R/T] is zero,
• If R0.L is less than 0x8000, the result is truncated to the value of R0.U.
• If R0.L is greater than 0x8000, the upper word is incremented (rounded up).
• If R0.L is 0x8000, R0 is half-way between two 16-bit numbers. In this case, rounding is
accumulator logic are used to round the resulting 16- or 32-bit value. If MACSR[S/U] is
cleared, the low-order 8 bits are used to round the resulting 32-bit fraction. If MACSR[S/U]
is set, the low-order 24 bits are used to round the resulting 16-bit fraction.
multiplying two 32-bit numbers creates a 64-bit product that is truncated to the upper 40
bits; otherwise, it is rounded using round-to-nearest (even) method.
based on the lsb of R0.U, so the result is always even (lsb = 0).
— If the lsb of R0.U = 1 and R0.L = 0x8000, the number is rounded up.
Fractional Operation Mode
Rounding
Table 4-2. Summary of S/U, F/I, and R/T Control Bits
S/U F/I R/T
0
0
0
1
1
1
0
1
1
0
1
1
MCF5235 Reference Manual, Rev. 2
x
0
1
x
0
1
Signed, integer
Signed, fractional
Truncate on MAC.L and MSAC.L
No round on accumulator stores
Signed, fractional
Round on MAC.L and MSAC.L
Round-to-32-bits on accumulator stores
Unsigned, integer
Signed, fractional
Truncate on MAC.L and MSAC.L
Round-to-16-bits on accumulator stores
Signed, fractional
Round on MAC.L and MSAC.L
Round-to-16-bits on accumulator stores
Operational Modes
Memory Map/Register Definition
4-9