Firmware Operation - FIGnition FUZE Hardware Reference Manual

The Serial RAM uses the same SPI interface and protocol as described in section 5.2.2.
The Serial RAM chip uses a different set of commands and FIGnition only uses a few of
them:
Cmd
WRSR (Write Status)
READ (Read bytes)
WRITE (Write Bytes)
The data in the Serial RAM chip is organized as a continual array of bytes, which wrap
around after every 8Kb on an 8Kb chip. Any byte can be directly addressed, read and writ-
ten. However, the chip can pretend the data is organized as pages of 32 bytes or even a
mode where bytes can't be sequentially read, and each byte must be read or written as a
separate command. To put the chip in the correct reading/writing mode FIGnition's firm-
ware begins by sending a WRSR command with its data byte value set to '64' (binary
01000000).

6.3 Firmware Operation

FIGnition's Serial RAM is mostly used to run user-written Forth programs. Forth programs
are not run by reading the text you see when you read or write a program. Instead, they
are first converted into a sequence of numbers; where each number is either a special
command code from 0 to 67 or the address of a command which contains a sequence of
command codes or other command addresses.
Forth then runs programs by locating the next command code (or command address);
reading it and then executing it.
Code
$01
$03
$02
Fig 6.2
Address Bytes
0
2 (The most sig-
nificant byte
comes first)
2
Data Bytes
1
1 or more... (data bytes
read in from the Serial
RAM chip)
1 or more... (data bytes
sent out from the Serial
RAM chip)