User manual

PICkit™ Serial Analyzer User’s Guide

EXEC manages the interface with the host. The data stream sent to PICkit™ Serial

Analyzer from the host is encoded with ECMD TAGs and the data stream returned to

the host from PICkit™ Serial Analyzer uses EDATA TAGs. Likewise, the COMM con-

troller utilizes another set of predefined TAG(s) - CCMD TAGs (outgoing scripts) and

CDATA TAGs (returning data). EXEC has no knowledge of COMM TAG(s) but simply

transports data blindly between the host and COMM using EXEC TAG(s). RAM buffers

are used as conduits to exchange data with COMM. Data destined for COMM is

queued in RAM buffer 1 (CBUF1). Data returning from COMM is funneled through RAM

buffer 2 (CBUF2).

The PICkit™ Serial Analyzer is designed to facilitate continuous ‘spooling’ of data

to/from the external serial device. Separate 255-byte circular buffers are maintained for

both outgoing data (scripts/data) and returning data. The USB interface is not permitted

to be a bottleneck in the PICkit™ Serial Analyzer operation. EXEC processes each

USB packet immediately. If data is destined for a RAM buffer, the host is responsible to

insure adequate room is available in the buffer before the data is sent to avoid a fatal

‘overrun’ error. Returning data is queued in the appropriate circular buffer until retrieved

by EXEC, tagged and sent to the host. It is possible to overrun the return buffer under

some circumstances but should be rare. EXEC can interleave EXEC data with COMM

data as necessary.

The PICkit™ Serial Analyzer maintains fixed-length blocks of data for CONTROL and

STATUS. The CONTROL_BLOCK provides ‘static’ configuration information. The

STATUS_BLOCK is a snapshot of the PICkit™ Serial Analyzer operation. Each block

is divided into three sections corresponding to EXEC, COMM (common to all protocols)

and COMM (specific to the active serial protocol).

TABLE 9-1: TAG BYTE TYPES

The other major blocks are the control memory block and the status memory block. The

control block is used to configure the PICkit™ Serial Analyzer. The control block is

divided into the following three sections:

• EXEC module configuration

• Generic COMM module configuration

• Protocol specific communication configuration

This third section will change depending on the protocol. The Status block keeps the

status of various flags and is similarly divided into three sections.

TABLE 9-2: CONTROL BLOCK

TAG types Definition

ECMD EXEC command TAG(s) – interpreted by EXEC

EDATA EXEC data TAG(s) – generated by EXEC

CCMD COMM command TAG)(s) – interpreted by COMM

CDATA COMM data TAG(s) – generated by COMM

TAG Bytes Definition

0-7 EXEC section

8-15 Generic COMM section

16-23 Protocol specific communication section