Cypress enCoRe V CY7C643 Series Technical Reference Manual Download Page 32

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enCoRe™ V CY7C643xx, enCoRe™ V LV CY7C604xx TRM, Document No. 001-32519 Rev *H

3. Supervisory ROM (SROM)

This chapter discusses the Supervisory ROM (SROM) functions. For a quick reference of all enCoRe V registers in address
order, refer to the

3.1

Architectural Description

The SROM holds code that boots a enCoRe V device, cali-
brates circuitry, and performs flash operations. The func-
tions provided by the SROM are called from code stored in
the flash or by device programmers.

The SROM is used to boot the part and provide interface
functions to the flash blocks.

Table 3-1

lists the SROM func-

tions. The SROM functions are accessed by executing the
Supervisory System Call instruction (

SSC

), which has an

opcode of 00h. Before executing the

SSC

, the M8C's accu-

mulator needs to load with the wanted SROM function code
from

Table 3-1

Attempting to access undefined functions (Reserved func-
tions) causes a

HALT

. The SROM functions execute code

with calls; therefore, the functions require stack space. With
the exception of Reset, all of the SROM functions have a
parameter block in SRAM that you must configure before
executing the

SSC

Table 3-2

lists all possible parameter block variables. The

meaning of each parameter, with regards to a specific
SROM function, is described later in this chapter. Because
the

SSC

instruction clears the CPU_F PgMode bits, all

parameter block variable addresses are in SRAM Page 0.
The CPU_F value is automatically restored at the end of the
SROM function.

The MVR_PP and MVW_PP pointers are not disabled by
clearing the CPU_F PgMode bits. Therefore, the POINTER
parameter is interpreted as an address in the page indicated
by the

MVI

page pointers, when the supervisory operation is

called. This allows the data buffer used in the supervisory
operation to be located in any SRAM page. (See the

RAM

Paging chapter on page 38

for more details regarding the

MVR_PP and MVW_PP pointers.)

Note

ProtectBlock and EraseAll (described on page

) SROM functions are

not listed in this table because they are dependent on external programming.

Note

CLOCK and DELAY are ignored and are reserved for future use.

Two important variables that are used for all functions are
KEY1 and KEY2. These variables are used to help discrimi-
nate between valid

SSCs

and inadvertent

SSCs

. KEY1 must

always have a value of 3Ah, while KEY2 must have the
same value as the stack pointer when the SROM function
begins execution. This is the SP (Stack Pointer) value when
the

SSC

opcode is executed, plus three. For all SROM func-

tions except SWBootReset, if either of the keys do not
match the expected values, the M8C halts. The SWBootRe-
set function does not check the key values. It only checks to
see if the accumulator's value is 00h.

The following code example puts the correct value in KEY1
and KEY2. The code is preceded by a

HALT

, to force the

Table 3-1. List of SROM Functions

Function Code

Function Name

Required

Stack Space

Page

00h

SWBootReset

01h