Force SYS68K/CPU-30 R4, Техническое справочное руководство

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Hardware Description SYS68K/CPU-30 R4 Technical Reference Manual
Page 42
3.5 The System PROM Area
The first two read cycles after reset of the microprocessor are operand
fetches of the Initial Interrupt Stack Pointer (ISP) and the Initial Program
Counter (IPC). These operands are always fetched from addresses
0000.0000
16
and 0000.0004
16
, respectively.
3.5.1 Initialization Special control logic in FGA-002 maps the Boot PROM (not the System
Flash Memory) down to this address to allow the 68030 to boot from a
single byte-wide PROM. This facilitates debugging and low-level
program development. However, when the initialization routines in the
Boot PROM are completed, control is transferred to the System Flash
Memory in such a way that the 68030 appears to have been booted from
the System Flash Memory, not the Boot PROM. For this reason, the
System Flash Memory must also have the ISP and IPC loaded at address
0000.0000
16
and 0000.0004
16
, respectively.
0000.0000
16
in System Flash Memory: Initial Interrupt Stack Pointer
0000.0004
16
in System Flash Memory: Initial Program Counter
3.5.2 Memory
Organization of
the System
PROM Area The data path of the System Flash Memory is 32-bit wide, separated into
4-byte paths. Each byte path is connected to one Flash Memory device.
3.5.3 Read/Write to
the System
Flash Memory Read cycles with any port size are allowed. Write cycles are flagged by
the FGA-002 Gate Array with BERR. A programmable bit within the
FGA-002 may be used to enable write operation to the System Flash
Memory. In this case the FGA-002 will respond with an asynchronous
data acknowledge (DSACK0, DSACK1). The write takes affect to the
System Flash Memory depending on switch SW5-4.
The status of SW5-4 is connected to PI/T #2.
Pin PC4 on the PI/T #2 interface signal protects the write to the System
Flash Memory and must be programmed as an input.
SW5-4 Description
OFF (default) Write to System Flash Memory enabled
ON Write to System Flash Memory disabled