The console's receive side, standing in for the console node until the
mesh exists, as CONSOLE-TX does for output. A data fetch (@, @+, @b)
from CONSOLE-STATUS gives -1 when a character is pending and 0 when
not; from CONSOLE-RX it gives the next character and takes it, or -1
with none pending. The characters come from a queue the test feeds.
Instruction words and literals are still fetched with v4_node_load, so
code at a register's address is never taken for the register.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
EMIT is a device service: a character sent to the console node. The
mesh and its ports are development step 2 and the memory map is open
(D-4), so the single-node model now stands in for the console with one
memory-mapped register, so that printing words can be run and their
output compared with v3's.
v4_node_console_attach(n, addr): after it, a store to word address
`addr` appends the low 8 bits of the value to a buffer on the node
(V4_CONSOLE_CAP characters, 4096 by default) and does not write memory;
a load from `addr` reads the memory word as before. Characters past the
capacity are counted in console_dropped and discarded. The hook is in
v4_node_store, which all four store opcodes use.
It is off by default: v4_node_reset detaches the console (address -1)
and empties the capture, so the ISA's behaviour and every existing test
are unchanged unless a console is attached. The address is the
caller's choice.
New test v4/tests/test_console.c, 22 checks per width: direct stores,
!b, ! and !+ through the executor printing "Hi!", memory at and around
the register untouched, the low byte only, overflow, detach, a console
at word 0, and reset. At 32- and 64-bit cells, optimised and ASan+UBSan
(`make test`, `make sanitize`); all other v4 tests still pass. Four
mutations of the hook each fail.
DECOMPOSITION.md section 7 gains the CONSOLE-TX row. No printing word is
defined here; EMIT and the words on it are still to do.
Test results on the amd64 host only. This is a development check, not
acceptance (JUSTIFICATION.md section 16).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
