MAC7200 datasheet(179/976 Pages) FREESCALE

179 / 976 page

Debug Application Usage

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

101

8.8.5

Debug Shift Register SC4

Please refer to Section 35.1.1, “JTAG Test Register (SC4)”.

8.8.6

Using the JTAG Interface

Because the JTAG interface requires internal clocks for synchronization, it is generally not safe to assume

that the interface is available all of the time. In particular, there are several situations where the JTAG

interface may not be available:

•

Immediately after a Power On Reset (POR)

•

Immediately after a loss of clock condition

In general, under normal operating conditions, the JTAG interface may be used while the RESET is

asserted for a normal system reset. The safest approach is to reset the device, program the debug registers,

and then reset the device again. Since the debug logic is not reset by a normal system reset, this procedure

is guaranteed to work.

In order to meet the IEEE 1149.1-1990 JTAG specification, it is required that the JTAG interface be run at

no faster than 1/8 the system clock frequency. As an example, for an 80MHz system, the maximum TCK

frequency is 10MHz. There may be further limitations introduced by the development system or PCB. If

the debug system does not seem to be functioning correctly, try reducing the JTAG speed and resetting the

system.

8.8.7

JTAG Pad Control

Control of the JTAG related pads is done purely from the PIM registers, as follows:

TCK

•

Can configure pull-up or pull-down

•

Can disable the TDI functionality. In this case, the pad becomes an output (driven low), and the

internal TDI signal is driven low (0).

TMS

•

Can configure pull-up or pull-down

•

Can disable the TDI functionality. In this case, the pad becomes an output (driven low), and the

internal TDI signal is driven low (0).

TDI

•

Can configure pull-up or pull-down

•

Can disable the TDI functionality. In this case, the pad becomes an output (driven low), and the

internal TDI signal is driven low (0).

TDO

•

Can configure slew rate

•

Can disable the TDO functionality. In this case, the pad becomes an input (All changes on the pad

are ignored by the system).

MAC7200 Datasheet(PDF) 179 Page - Freescale Semiconductor, Inc

MAC7200 Datasheet(HTML) 179 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL