Tadpole SPARCbook 3 series, Reference Manual

Page: 191 / 216

Microcontroller Subsystem
12-11
Command Set
12.2.3 Read/Write/Modify Commands
These commands are used to read or modify the byte attribute addressed.
Each command uses the same form, where the value written to the attribute
is given by:
new_attribute = (old_attribute AND mask) EOR value
The old attribute value is returned in all cases. Therefore, to read an
attribute the parameters are:
mask = 0xff, value = 0
For example, to write an attribute to 0x5A, the parameters are:
mask = 0x00, value = 0x5A
To change bit n to value v (either 1 or 0) while leaving all other bits
unchanged:
mask = NOT(1<<n), value = (v<<n)
The following table summarizes the Read/Write/Modify Commands
Opcode Command Argument Returned Function
0x20 Control LCD mask ack + 2 bytes The host controls the LCD via this command.
Setting a bit activates the approriate symbol on the
unit's LCD panel.
Bit 0 Caps lock
Bit 1 Scroll lock
Bit 2 Numlock
Bit 3 Disk active
Bit 4 LAN active
Bit 5 WAN active
Bit 6 PCMCIA active
Bit 7 DC OK
Bit 8 Compose
0x21 Control Bitport mask ack + 1 byte The microcontroller administers several bit ports
which are used to control things within the system.
Setting a bit in the bitport sets the corresponding
signal to a high level. The power-up signal setting is
given in parentheses.
Bit 1 TFTPWR - S3XP TFT power (high)
Bit 2 SYNCINVA - external monitor sync (low)
Bit 3 SYNCINVB - external monitor sync (low)
Bit 4 BP_DIS - bootprom disable via TS102 -
boot from PCMCIA. (low)
Bit 5 ENCSYNC - enable composite sync (low)
Table 12-2 Read/Write/Modify Commands
S3GX_TRMBook Page 11 Friday, September 19, 1997 11:39 am