NXP Semiconductors Kinetis KE1xZ256, Reference Manual

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Table 13-7. Peak request formula operands
Operand Description
PEAKreq Peak request rate
freq System frequency
entry Channel startup (4 cycles)
read_ws Wait states seen during the system bus read data phase
write_ws Wait states seen during the system bus write data phase
exit Channel shutdown (3 cycles)
13.4.4.3 eDMA performance example
Consider a system with the following characteristics:
• Internal SRAM can be accessed with one wait-state when viewed from the system
bus data phase
• All internal peripheral bus reads require two wait-states, and internal peripheral bus
writes three wait-states viewed from the system bus data phase
• System operates at 150 MHz
For an SRAM to internal peripheral bus transfer,
PEAKreq = 150 MHz / [ 4 + (1 + 1) + (1 + 3) + 3 ] cycles = 11.5 Mreq/sec
For an internal peripheral bus to SRAM transfer,
PEAKreq = 150 MHz / [ 4 + (1 + 2) + (1 + 1) + 3 ] cycles = 12.5 Mreq/sec
Assuming an even distribution of the two transfer types, the average peak request rate
would be:
PEAKreq = (11.5 Mreq/sec + 12.5 Mreq/sec) / 2 = 12.0 Mreq/sec
The minimum number of cycles to perform a single read/write, zero wait states on the
system bus, from a cold start where no channel is executing and eDMA is idle are:
• 11 cycles for a software, that is, a TCDn_CSR[START] bit, request
• 12 cycles for a hardware, that is, an eDMA peripheral request signal, request
Functional description
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
250 NXP Semiconductors