ST20-GP6 datasheet(79/123 Pages) STMICROELECTRONICS

79 / 123 page

ST20-GP6

79/123

14.4 Controlling the diagnostic controller

This section gives a summary of host communications with the diagnostic controller.

The diagnostic controller has direct access to:

•

the instruction pointer,

•

a selection of CPU state control signals,

•

the memory bus,

•

memory-mapped peripheral conﬁguration registers.

This access does not depend on the state of the CPU. Access to non-memory-mapped peripheral

conﬁguration registers is via the CPU, and for this the CPU must be active and running the appro-

priate handler.

The host can give two commands to the diagnostic controller:

peek and poke. Peek reads memory

locations or conﬁguration registers, and

poke writes to memory locations or conﬁguration registers.

The diagnostic controller responds to a

peek command with a peeked message, giving the con-

tents of the peeked addresses.

The diagnostic controller has registers, which are accessed from the host using

peek and poke

commands. The registers are used to control breakpoints, watchpoints, datawatch, tracing and

other facilities.

The target CPU can also access these registers using the normal device load and store instruc-

tions, so the target software running on the CPU can program its own diagnostic controller. A lock

is provided to prevent CPU access, which can be released by the diagnostic controller when a

breakpoint or watchpoint match occurs.

In addition, the target CPU can

peek and poke the host via the diagnostic controller by reading or

writing addresses in the top half of the memory space of the diagnostic controller. This facility can

be disabled.

Various different types of CPU events can be selected as

trigger events. When an trigger event

occurs, the diagnostic controller can send a

triggered message.

The four types of message are summarized in Table 14.1. The messages are distinguished by the

two least signiﬁcant bits of the message header byte.

Messages may be initiated from either the host or the target. Target initiated messages, which con-

stitute asynchronous or unsolicited messages, can be enabled by a property bit.

Messages are composed of a header byte followed by zero or more data bytes, depending on the

type of message. The formats for the four message types are shown in Figure 14.2.

Message type

Direction

Bit 1

Bit 0

Meaning

poke

Command.

Write to one or more addresses.

peek

Command.

Read from one or more addresses.

peeked

Opposite to

peek command.

The result of a

peek command.

triggered

DCU to host.

A trigger event has occurred.

Table 14.1 Types of diagnostic controller message

ST20-GP6 датащи(PDF) 79 Page - STMicroelectronics

ST20-GP6 датащи(HTML) 79 Page - STMicroelectronics

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

датащи скачать

ссылки URL