MAC7200 datasheet(222/976 Pages) FREESCALE

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External Signal Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

144

Freescale Semiconductor

11.9.3

Pin Protocol

The protocol for the ARM7 processor transmitting messages via the auxiliary pins shall be accomplished

with the MSEO pin(s) function (outlined in Table 11-15).

MSEO is used to signal the end of variable-length packets, and not fixed length packets. MSEO is sampled

on the rising edge of the message clock (MCKO).

TCK

The Test Clock (TCK) input pin is used to synchronize the test logic, and control register

access through the JTAG port.

TRST

The optional Test Reset (TRST) input pin is used to asynchronously initialize the JTAG

controller. The TRST pin has an internal pull-up resistor.

Table 11-14. A7S Nexus3 Auxiliary Pins

Auxiliary Pins

Input/

Output

Description of Auxiliary Pins

MCKO

Message Clock Out (MCKO) is a Nexus generated output clock to development tools for

timing of MDO & MSEO pin functions. MCKO is programmable through the DC Register.

MDO[N:0]

Message Data Out (MDO[N:0]) are output pins used for OTM and BTM. External latching of

MDO shall occur on rising edge of the Nexus3 message clock (MCKO).

MSEO[1:0]

Message Start/End Out (MSEO) are output pins which indicate when a message on the

MDO pins has started, when a variable length packet has ended, and when the message

has ended. External latching of MSEO shall occur on rising edge of the Nexus3 clock

(MCKO). One or two pin MSEO functionality is determined at integration time.

RDY

Ready (RDY) is an output pin used to indicate to the external tool that the Nexus block is

ready for the next Read/Write Access. If Nexus is enabled, this signal is asserted upon

successful (without error) completion of an AHB transfer (Nexus read or write) & is held

asserted until the JTAG state machine reaches the “Capture_DR” state. Upon exit from

system reset or if Nexus is disabled, RDY remains de-asserted.

EVTO

Event Out (EVTO) is an output which, when asserted, indicates one of two events has

occurred based on the EOC bits in the DC Register. EVTO is held asserted for one (1) cycle

of MCKO:

1) one of four watchpoints has occurred & EOC = 2'b00

2) debug mode was entered (DBGACK from ARM7) & EOC = 2'b01

EVTI

Event In (EVTI) is an input which, when asserted, will initiate one of two events based on

the EIC bits in the DC Register (if the Nexus module is enabled at reset; see

Section 11.1.3.3, “Disabled”):

1) Program Trace synchronization messages (provided Program Trace is enabled & EIC =

2'b00).

2) Debug request (EDBGRQ) to ARM7 EmbeddedICE module (provided EIC = 2'b01 and

this feature is implemented).

Table 11-13. JTAG Pins for A7S Nexus3 (Continued)

JTAG Pins

Input/

Output

Description of JTAG Pins (included in ARM7 CPU)

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