RCA RMB-167 - Manual (Page 27)

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8 BOOTSTRAPPING
The RMB-167 bootstrapping is triggered by grounding P0L.4 at reset. A 16 pin header is used to
ground the bits of P0L via a resistor array with a nominal value in the range of 22K to 33K.
Note that the GAL which controls the bootstrap load operation is also responsible for turning on
the LED. In its default implementation, the LED is lit once the RSTOUT# signal is activated. For
specific applications, the user may alter the operation of the bootstrap logic by changing the GAL
equations.
Once the bootstrap loader is invoked the serial port S0 is used to communicate with the C167.
The host must first send a 0 byte with 8 data bits, 1 stop bit and no parity bits. The C167
responds with the byte A5h . Then the host expects 32 bytes of code to be downloaded to
internal RAM starting at address 0FA40h and run.
Since 32 bytes is not enough to initialize and configure the C167 and then download a user
program, a secondary loop is used. This loop is a short piece of code that is placed starting at
address 0FA60h, so that when the 32 bytes of primary code are executed, the program continues
with the secondary loop. The approach is described in more detail below.
The 32 bytes downloaded are, in hexadecimal,
E6 F0 60 FA
9A B7 FE 70
A4 00 B2 FE
7E B7
B4 00 B0 FE
86 F0 BB FC
3D F6
CC 00
CC 00
CC 00
CC 00
which correspond to the following short code.
; origin is 0FA40h
mov R0, #0fa60h
W0:
jnb S0RIR, W0
movb [R0], S0RBUF
bclr S0RIR
movb S0TBUF, [R0]
cmpi1 R0, #0fcbb
; read 604 bytes
jmpr cc_NE, W0
nop
nop
nop
nop