MC9328MX21 Datasheet, PDF (64/106 Pages) Motorola, Inc – i.MX family of microprocessors

Specifications
Table 37. System Clock Requirements
Main Clock Frequency (MHz)
13
16.8
Clock divide ratio
Generated frequency (MHz)
Relative time imprecision
13
17
1
0.9882
0
0.0117
19.44
19
1.023
0.023
This shows that the user should take care of the main clock frequency when using the one-wire module. If
the main clock is an exact integer multiple of 1 MHz, then the generated frequency will be exactly 1 MHz.
NOTE:
A main clock frequency below 10 MHz might cause a misbehavior of the module.
3.18 USB On-The-Go
Four types of data transfer modes exist for the USB module: control transfers, bulk transfers, isochronous
transfers and interrupt transfers. From the perspective of the USB module, the interrupt transfer type is
identical to the bulk data transfer mode, and no additional hardware is supplied to support it. This section
covers the transfer modes and how they work from the ground up.
Data moves across the USB in packets. Groups of packets are combined to form data transfers. The same
packet transfer mechanism applies to bulk, interrupt, and control transfers. Isochronous data is also moved
in the form of packets, but because isochronous pipes are given a fixed portion of the USB bandwidth at
all times, there is no end-of-transfer.
MC9328MX21 Product Preview, Rev. 1.1
64
Freescale Semiconductor