1 2 3 4
next5..v_wxyz
next
next
400v_wxyz
next
next
5..v_wxyz rdata
next
rdata
ubfx
CYCLE RULER
hclk
BME AHB Input Bus
mx_haddr
mx_hattr
mx_hwrite
mx_hwdata
mx_hrdata
mx_hready
BME AHB Output Bus
sx_haddr
sx_hattr
sx_hwrite
sx_hwdata
sx_hrdata
sx_hready
BME States + Datapath
control_state_dp1
control_state_dp2
reg_addr_data_dp
Figure 17-8. Decorated load: unsigned bit field insert timing diagram
The decorated unsigned bit field extract follows the same execution template shown in
the above figure, a 2-cycle read operation:
• Cycle x, 1st AHB address phase: Read from input bus is translated into a read
operation on the output bus with the actual memory address (with the decoration
removed) and then captured in a register
• Cycle x+1, 2nd AHB address phase: Idle cycle
• Cycle x+1, 1st AHB data phase: A bit mask is generated based on the starting bit
position and the field width; the mask is AND'ed with the memory read data to
isolate the bit field; the resulting data is captured in a data register; the input bus
cycle is stalled
• Cycle x+2, 2nd AHB data phase: Registered data is logically right shifted for proper
alignment and driven onto the input read data bus
NOTE
Any wait states inserted by the peripheral slave device
(sx_hready = 0) are simply passed through the BME back to the
master input bus, stalling the AHB transaction cycle for cycle.
Chapter 17 Bit Manipulation Engine (BME)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 283
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